Doctoral Degrees (Animal Sciences)

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Application of dietary bentonite clay as feed addictive on feed quality, water quality and production performance of African catfish (Clarias gariepinus)
(Stellenbosch : Stellenbosch University, 2016-03) Ayoola, Mathew Oluwaseyi; Salie, Khalid; De Wet, Lourens; Stellenbosch University. Faculty of Agrisciences. Dept of Animal Sciences.
ENGLISH ABSTRACT: Aquaculture remains the fastest growing animal food producing sector and is gradually overtaking capture fisheries as a source of food fish. The challenges of poor feed quality, feed utilisation and water quality are recurring issues that hinder the growth of aquaculture industry. This study investigated the effects of natural bentonite (NB) and its acid activated form (AB) as feed additives on aquafeeds with reference to the physical quality, growth performance, gut evacuation rate and water quality with African catfish (Clarias gariepinus) as the experimental species. Bentonite clay has found application as a feed additive in animal science and aquaculture. It is used as a mycotoxin binder to improve feed utilisation. Application of dietary activated bentonite form is yet to be fully elucidated to the best of our knowledge. Aquafeeds’ physical qualities, including water stability, feed durability, feed bulk density and nutrient leaching, were investigated. Dietary bentonite clay was added to commercial aquafeeds and each treatment were replicated four times. Water stability, feed durability, feed bulk density and nutrient leaching were all significantly affected (p<0.05) by treatments. Measured parameters (water stability, feed density and feed durability) increased (p<0.05) with the quantity of AB in the clay blend and at high inclusion level as compared to control. Values increased with an increased inclusion level of clay in feed, while nutrient leaching value decreased with quantity of AB and high inclusion. AB had higher values as compared to NB and the control. These results validated the potential utilisation of NB and AB as feed binders. Their ability to improve pellet physical qualities is expected to enhance feed utilisation, maintain good water quality and increase fish growth. Aquafeeds with bentonite clay blend, and each at different inclusion levels improved (p<0.05) growth performance, feed conversion ratio (FCR), specific growth rate (SGR), red blood cell (RBC), and haematocrits (HCT). Parameters improved with an increase in quantity of natural bentonite and at low inclusion level. Growth performance increased (p<0.05) as compared to control with bentonite inclusion up to 1500 mg/kg and decline at 3000 mg/kg. The contents of crude protein (CP), fat, moisture, ash and abdominal fat in the whole body composition were significantly affected (p<0.05) by the treatment diets. Abdominal fat and tissue fat content increased with bentonite inclusion. To evaluate the effect of NB and AB on gut evacuation rate of Clarias gariepinus, fish were randomly allocated to treatment diets and fed ad libitum. Four (4) fish were randomly selected per treatment to measure post feeding stomach content (SC) and intestinal filling (IC) content at (5, 30, 60 and 120 min). The control diet had higher values for SC at 5 min which differed significantly (p<0.05) as compared to clay diets. SC decreased (p<0.05) with time in all diets and clay diets had higher value (p<0.05) between (30 – 120 min) as compared to control. In clay diets, SC decreased faster over time with reduced quantity of AB and low inclusion level. The IC of control diets had higher values (p<0.05) over time as compared to clay diets. The water quality parameters (pH, N02-, NH3-N and TSS) were evaluated in a static aerated tank. Aquafeeds were fed to adult fish at 3% body ratio twice daily. Each treatment diet was replicated four (4) times, and 10 fish were randomly allotted to each tank. The water temperature was 25 ± 2°C and dissolved oxygen (DO) was 3-9 mg/L. Water samples were collected daily from each tank. In phase I, water quality was evaluated over seven (7) days, and in phase II over five (5) days. No mortality was recorded during the study. The values of pH, N02-, NH3-N and TSS increased significantly (p<0.05) in all treatment diets over time. In both phases, clay treated diets had lower values for measured parameters (p<0.05) compared to those of control. In clay diets, values increased (p<0.05) with quantity of AB and high inclusion level. Fish feed intake reduced as water quality deteriorated, and uneaten feeds contributed to increase in poor water quality. Thus, high water stability of clay treated diets attributed to maintenance of good water quality as compared to the control. The results showed that dietary clay enhanced feed binding, which affected digesta viscosity. This reduced the rate of feed evacuation in the gut, and, thus, enhanced proper breakdown and absorption of nutrients. Higher inclusion levels of bentonite clay and increased quantity of AB are not suitable for improved growth and feed utilisation, as increased in digesta viscosity led to fermentation in the gut. An optimum level of performance was recorded at 1500 mg/kg inclusion with natural bentonite (B1500) with a significantly (p<0.05) better performance as compared to control and acid activated bentonite. A clay combination blend up to 50% (A50B50) at low inclusion level (500 mg/kg) of acid activated bentonite is considered optimum.
The application of genomics and transcriptomics for the characterization of the genetic diversity of tick-resistance in Angus, Brahman, Nguni, and Santa Gertrudis cattle artificially infested with Rhipicephalus microplus and Rhipicephalus decoloratus
(Stellenbosch : Stellenbosch University, 2022-04) Marima, Jacqueline Keena; Dzama, Kennedy; Jonsson, Nicholas N.; Dube, Bekezela; Marufu, Munyaradzi Christopher; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: Tick resistance is a complex polygenic trait that is governed by immuno-genetic mechanisms that are currently not fully understood. It is, however, currently accepted that the Bos indicus, Zebu and Sanga breeds, which are better adapted to the harsh environmental conditions of the tropical and subtropical regions, often exhibit superior tick resistance as opposed to their Bos taurus counterparts. Breeding for natural host resistance presents a transformational alternative for tick control that will see cattle production industries move away from the excessive and often incorrect usage of chemical acaricides for tick control. However, selective breeding for this trait using tick count data, which varies according to the environment, is unreliable and often produces variable results. Marker-assisted selected breeding and the development of accurate prediction tests with practical feasibility in the field will enhance the accuracy of selection and increase genetic gains. Omics technologies, including transcriptomics, genomic and proteomics are tools that have been instrumental in uncovering putative genes, pathways, and potential biomarkers in cattle. Despite the progress made, there is still a lot that remains misunderstood about the tick resistance trait. Further studies are required. While previous studies have investigated tick resistance in the different breeds and tick species in isolation of each other, in this study a comparison between two tick species (Rhipicephalus microplus and R. decoloratus) and three cattle breeds of different lineages was presented; the Bos indicus Brahman breed, the Bos taurus Angus breed and the indigenous Bos taurus africanus Nguni breed. The differentially expressed genes and their single nucleotide polymorphisms (SNPs) genotypes were of particular interest when studying the different host tick associations presented in this study. The study also included the transcriptome analysis of samples from the Santa Gertrudis, a composite breed recognised for its superior tick resistance while simultaneously boasting good reproductive and production efficiency and meat quality. Using a 150K Bovine SNP chip to genotypes samples from the Angus, Brahman and Nguni breeds, the SNP genotypes, allele frequencies and dosages of SNPs of 37 candidate genes were determined. A total of 257 SNPs were discovered but the SABT2 gene produced a SNP (ARS-BFGL- NGS-94983) that showed a significant correlation with tick count and significantly different allele frequencies between breeds. No functional information regarding the role of the SATB2 gene in host resistance to tick, their further investigations are warranted. The microarray analysis of blood samples from Santa Gertrudis cattle artificially infested with the invasive R. microplus tick species revealed variable levels of tick resistance accompanied by variable gene expression profiles across the tick-resistant and tick-susceptible phenotypes. It was evident that upon long term exposure to the R. microplus the tick-resistant Santa Gertrudis cattle displayed an increased ability to develop and mount more robust adaptive responses against the tick infestations than the tick-susceptible animals Lastly, the RNA sequencing study allowed the identification of several putative genes that have featured in previous studies of tick resistance in cattle. Using inter-breed and inter-tick species contrast across the Angus, Brahman, and Nguni cattle breeds as well as between the R. microplus and R. decoloratus tick species, variable gene expression profiles were observed. The CCL26 and MZB1 appeared as two of the factors to note in the inter-tick species comparisons, while the MMP12 gene was identified in the inter-breed comparison. The Nguni breed produces significantly different gene expression patterns than both the Angus and the Brahman breeds. The differential expression of the highlighted gene led to the conclusion that tick resistance is not only characterised by innate and adaptive immune responses but there are other crucial role players, presented in this study as components of the extracellular matrix. The three studies included here inform further investigations into the roles of the highlighted genes and SNPs to further elucidate the complex phenotype of host resistance to ticks.
Aquaculture practices in irrigation reservoirs of the Western Cape Province of South Africa in relation to multiple resource use and socio-ecological interaction
(Stellenbosch : Stellenbosch University, 2014-04) Salie, Khalid; Rana, Krishen; Brink, Danie; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: Aquaculture has proven to be a viable operation in multi-used irrigation reservoirs (also referred to as farm dams) in the Western Cape province (WCP) of South Africa. Many studies found that the fitness-for-use of these reservoirs for both net cage culture of fish and irrigation of crops is feasible. However, practising intensive fish farming in existing open water bodies can increase the nutrient levels of the water through organic loading, originating from uneaten feeds and fish metabolic wastes. Under such conditions the primary (irrigation) and secondary (drinking water and recreation) usage of the dam could be compromised by deteriorating water quality. Rainbow trout (Oncorhynchus mykiss) farming is done in Mediterranean climatic conditions of the WCP. This type of climate presents short production seasons with fluctuating water quality and quantity. The study investigated the dynamics of water physico-chemical parameters and assessed the long term impact of rainbow trout farming on irrigation reservoirs. Furthermore, associated land-use in the catchment of such integrated aqua-agriculture systems is described, and mitigation to minimise the impact of fish farming evaluated. The investigation concluded with assessing the contribution of aquaculture to rural and peri-urban communities. The aim is to present an integrated, socio-ecologically balanced farming system for irrigation reservoirs with associated aquaculture activities. A total of 35 reservoirs, including both fish farming and non-fish farming ones, were selected as research sites. They were located in three geographical regions namely, Overberg (Grabouw/Caledon), Boland (Stellenbosch/Franschhoek) and Breede River (Ceres/Worcester). Reservoirs were <20 ha in surface area and the volume ranges from 300 000 to 1 500 000 m3. Water samples were collected monthly and seasonally for the different investigations and analysed for a range of water quality parameters, including: transparency (Secchi disc), temperature, dissolved oxygen (DO), pH, sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), chloride (Cl), carbonate (CO3), bicarbonate (HCO3), manganese (Mn), copper (Cu), zinc (Zn), boron (B), total phosphorous (TP), orthophosphate (PO4), total ammonia nitrogen (TAN), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), aluminium (Al), total suspended solids (TSS), total dissolved solids (TDS), alkalinity, hardness and sulphate. Phytoplankton samples were also collected, genera identified and biomass calculated. The water quality data were analysed in terms of surface and bottom strata in both fish farming and non-fish farming reservoirs based on repeated measurements at the same site location at different times using the procedure General Linear Models of Stastical Analysis System (SAS, 2012). Values p<0.05 were considered as statistically significant. A Principal Component Analysis (PCA) biplot was used to graphically depict all the sites and measured water quality variables with the purpose of trying to see whether the fish farming and non-fish farming ones showed any groupings and how the sites were related to the measured variables. Structured questionnaires and informal discussions were used to collect additional information on the water use, production data and socio-economic effects on fish farmers. Categorical data gathered from the interviews (21 aquaculture projects) were analysed for frequency of occurrence using the Statistical Product and Service Solutions (SPSS) computer programme (SPSS Systems for Windows, Version 12.0). Results are presented in publication form with research chapters focusing on the subject areas of water quality impact, catchment land-use, potential mitigation measures and aquaculture contribution. Results for the water quality analyses indicated that as a collective, the farm reservoirs’ overall minimum, mean and maximum values for the physico-chemical parameters were fit-for-use for trout farming. The depth of the reservoirs ranged from 1.2 - 21.6 m with the low value taken during the summer season. Values lower than 5.0 m can cause management problems for floating cages that require a minimum of 4.0 m for net suspension and 1.0 m of free space below for adequate lateral flow. The Secchi disc reading of the reservoirs ranged from 10 – 510 cm. Higher transparencies were recorded after the winter rains when sand, silt and clay settled. Trout feeding is dependent on visibility and transparencies of more than 50 cm are required for good feeding conditions. The dissolved oxygen (DO) ranged from 0.3 – 16.4 mg/L with values below 5.00 mg/L recorded during summer when extraction and temperatures were high and provided conditions unable to sustain trout farming. The situation reverses with the onset of winter when the dams fill and DO rises above 5.00 mg/L as required for trout farming. The phosphorous (P) levels ranged from 0.001 – 0.735 mg/L. Higher concentrations were recorded during the winter turnover phase when bottom and surface waters mixed. Concentration above 0.01 mg/L can cause eutrophication of the water bodies. Total ammonia nitrogen (TAN) ranged from 0.015 - 6.480 mg/L. Higher concentrations were recorded during summer when temperatures were high and depths were low. TAN can be toxic to fish when the pH and temperature are high. The generally low least square means (LSM) for TAN were indicative of minor environmental impact of trout farming operations conducted during the colder, winter rainfall months. Trout farming coincided with conditions where the water temperatures were low, dam levels were high and dams were overflowing. The difference in bottom and surface water quality of reservoirs and the site location were found to be more important than the absence or presence of fish farming. The difference in bottom and surface water is directly linked to the ecological status of the sediment, which serve as nutrient sinks. In monomictic dams found in Mediterranean areas, mixing occurs during the winter turnover phase. Nutrients are released due to surface and bottom water mixing, brought about by torrential rains and wind turbulence. The concentration of organic material in the sediment and bottom waters is a function of the nutrient loading over time, irrespective whether the non-point sources were fish farming or agricultural activities and therefore it is difficult to partition causes and effects. In cases where reservoirs were already eutrophic due to past agricultural practices, implementing aquaculture could exacerbate the poor water quality status of the reservoir. There was a statistically significant difference between fish farming and non-fish farming for phosphorous, Secchi disc, total suspended solids and nitrite-nitrogen (p<0.05) and no statistically significant difference between fish farming and non-fish farming for dissolved oxygen, total ammonia nitrogen and nitrate-nitrogen (p>0.05). There was a statistically significant difference between surface and bottom waters for P and TAN (p<0.05). One reason for higher P and TAN concentrations in bottom waters is the accumulation of both in the sediment and subsequent release in the water column when the water mixes. A two-dimensional scatter plot was generated using the score for the first two principal components. The first two principal components accounts for 40 and 17 % of the total variance respectively, and the two groups of fish farming and non-fish farming did not separate well based on the first two principal components. The occurrence and distribution of phytoplankton biomass fluctuated with dam water levels and nutrient concentrations. The prevailing phytoplankton communities are important to fish farmers for two reasons: 1. It leads to fluctuations in dissolved oxygen concentrations via users (respiration and decomposition) and producers (photosynthesis). 2. It could lead to algal taint of fish flesh when geosmin-producing phytoplankton species are present. The frequency of occurrence indicated that the Group Chlorophyta (including genera, Chlamydomonas, Closterium, Oocystis, Scenedesmus, Staurastrum, Tetraedron, etc) had the most occurrences (n=371) with Chrysophyta (including genera, Dinobryon, Mallomonas, Synura, etc) the least (n=34). There was a statistically significant difference between genera occurrence and season (p<0.05). The geographical location of sites had no significance influence on the frequency of phytoplankton occurrence. There was no direct link between water quality and production yield (p>0.05). The fish yield of farms were linked mainly to the quality of fingerlings and the feed conversion ratio (FCR) achieved (p<0.05). Land-use patterns in the catchment where fish farming dams were located have shown that the dams are multiple-used systems. The ecological integrity of the farm dam ecosystem is dependent on the base volume. The dam is primarily for irrigation and fish farming can be compromised when higher demand for water is required during the dry season. The dams receive about 20 % of its water from rainfall and the rest from runoffs. Farmers could not provide accurate extraction rates making it difficult to predict water levels for future fish production. Four potential mitigation measures to reduce nutrient loading were described namely, feed management (quantity, frequency, type, etc.), feeding method (demand feeders, hand feeding), feed ingredients (formulation) and floating gardens. Both feed management procedures and demand feeders were evaluated as to the efficiency of reducing feed wastage and optimising FCR’s. The small-scale fish farmers were producing approximately 6 tons and had an average FCR of 1.96:1 ± 1.15. If farmers could improve their FCR’s by 0.1 (i.e. from 1.96 to 1.86), it would translate into a reduction of 100 kg feed for every ton of fish produced and result in 5% decrease in nutrient loading. The results of the water analysis and visual assessment of faecal length and colour showed no statistically significant difference between treatments for the guar-gum based binder (p>0.05). In addition, the level of binder did not influence digestibility of the experimental diets. The floating garden study indicated that it was feasible to construct a low cost raft system that is easy to manage and can produce plant crops as a hydroponic system in conjunction with fish farming cages. The lettuces grown on farm dam water provided support for the premise that the water quality can be improved via extraction of nutrients for crop production. For the production of 3.5 kg/m2 lettuce, a ratio of 1.09 plants/fish equal to 1.84 g feed/day/plant would reduce the accumulation of soluble nutrients around floating net cage farming system. The socio-economic evaluation of the contribution of fish farming to the welfare of rural and peri-urban farming communities supported the notion that aquaculture can lead to the upliftment of participating communities. Seventy-one percent (71%) of the respondents indicated that their motivation for exploring aquaculture is to supply fish to the wholesale market in order to generate income. Sixty-one percent (61%) of the respondents conducted the sales themselves or co-opted family members to assist them. The contribution of aquaculture provided direct benefits through improvement in household income, subsistence food supply and skills development. Indirect benefits included providing an information hub for other emerging farmers, elevation of the fish farmer’s status in the community through greater wealth and knowledge creation and promoting sector diversification through new products and technology. The three main constraints to the promotion and growth of aquaculture were listed as lack of government support, insufficient market intelligence and access, and limited choice in the availability of suitable candidate aquaculture species. Irrigation reservoirs in the WCP have a history of enrichment through external sources supplying water via agricultural runoff (fertilisers and pesticides), catchment runoff (leaf litter and organic debris) and stormwater effluent (grey and black water). The incorporation of aquaculture into such dams adds extra nutrients to the water column and management is crucial to limit the nutrient loading and ensure environmental sustainability. Such an approach will ensure that commercial land-based crop farmers’ irrigation regime and water distribution operations would not be negatively affected. Therefore future research needs should focus on; firstly the prevention and minimisation of pollution deriving from aquaculture through improved production management and technology transfer, secondly the monitoring and evaluation of the catchment ecosystem as a continuum with all the external factors affecting the ecology of farm dams and thirdly, evaluating the sediment processes and dynamics as sinks for nutrient accumulation.
Beef production and biopreservative effects of dietary citrus and winery by-products
(Stellenbosch : Stellenbosch University, 2020-04) Tayengwa, Tawanda; Mapiye, Cletos; Dugan, Michael E. R.; Mutsvangwa, Timothy; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: The overall objective of the current study was to compare citrus pulp and grape pomace as dietary supplements and biopreservative for beef production and quality. Angus steers were fed 150 g/kg of dried citrus pulp (DCP) or grape pomace (DGP) as alternative fiber sources to wheat bran (control). Twenty-four steers (7 months old) were assigned to three dietary treatments (8 steers/ treatment) in a completely randomized design. Steer was the experimental unit. Steers were adapted for 21 d before 7 d of collecting feed, refusals, faecal and urine samples for determination of nutrient digestibility and utilisation. The digestibility trial was followed by a growth performance trial, which lasted 90d. During this period, dry matter intake (DMI), average daily gain (ADG) and feed efficiency data were collected. Post-feeding, steers were slaughtered and the left longissimus thoracis lumborum (LTL) from each carcass was sampled for physico-chemical meat quality attributes, shelf-life, major pro-oxidant fatty and volatile compound analyses, while the right LTL was sampled for the evaluation of eating quality attributes. Overall, steers fed the DGP diet had the greatest intake of dry matter (DM), organic matter (OM), crude protein (CP), ash free neutral detergent fiber (aNDFom), ether extract and starch followed by steers fed the DCP and control diets (P ≤ 0.05). Apparent digestibilities of DM, OM and aNDFom were greater (P ≤ 0.05) for the DCP diet compared to the DGP and control diets. Feeding the DCP and DGP diets increased (P ≤ 0.05) ruminal concentrations of total volatile fatty acids, acetate, isovalerate, acetate to propionate ratio, and reduced propionate concentrations compared to the control diet. The steers fed the control diet had the greatest urinary excretions of allantoin, uric acid and total purine derivatives followed by those fed the DCP and DGP diets (P ≤ 0.05). The nitrogen (N) intake, faecal nitrogen, N retention and N efficiency utilization were DGP > DCP > control diets (P ≤ 0.05). Feeding the DGP and DCP diets resulted in greater (P ≤ 0.05) ADG and final weight compared to the control diet. Steers fed the DGP diet had greater (P ≤ 0.05) DMI, warm and cold carcass weights than those fed the DCP and control diets. Shear force and income over feed costs were greatest for the DGP diet followed by the DCP and control diets (P ≤ 0.05). The DCP diet resulted in the greatest concentration of α-tocopherol in beef muscle tissues, followed by DGP and control diet (P ≤ 0.05). The beef antioxidant activity was DGP > DCP > control (P ≤ 0.05). During retail display DGP- or DCP-fed beef had greater L* (P ≤ 0.05) and fewer (P ≤ 0.05) coliforms than control diet fed beef. Beef TBARS and carbonyl contents were DGP < DCP < control (P ≤ 0.05). Overall, antioxidant activity decreased (P ≤ 0.05) while bacterial loads, TBARS and carbonyl contents increased (P ≤ 0.05) during retail display regardless of the diet. Feeding the DGP or DCP diets increased (P ≤ 0.05) the proportions of 18:2 n-6, 18:3 n-3 and total polyunsaturated fatty acid (FA) in LTL muscle. Beef from steers fed the control diet had greater (P ≤ 0.05) concentrations of alcohol, ketones and aldehydes, and lower (P ≤ 0.05) concentrations of sulphur containing compounds compared to the DCP- and DGP-fed beef (P ≤ 0.05). Feeding the DGP and DCP diets produced about 10% less tender (P ≤ 0.05) beef than the control diet. Overall, DGP improved nutrient intake, retention and efficiency of N utilization, growth performance, carcass attributes, beef shelf life, increase proportions of the main pro-oxidant fatty acids, and reduced aldehydes, ketones and alcohols associated with oxidation without compromising beef physicochemical and sensory quality. The current finding suggests that DGP may be a better fiber substitute and natural preservative in beef finishing diets than DCP.
Beef production and quality of Malawi Zebu steers fed diets containing rangeland-based protein sources under feedlot conditions
(Stellenbosch : Stellenbosch University, 2018-03) Chingala, Gregory; Mapiye, Cletos; Raffrenato, Emiliano; Dzama, Kennedy; Hoffman, Louwrens C.; Stellenbosch University. Faculty of AgriSciences. Department of Animal Sciences.
ENGLISH ABSTRACT: The current study evaluated smallholder farmers perceptions towards climate change, their identification of potential protein sources during drought, the nutrition profile of these protein sources and their actual production value when fed to Malawi Zebu steers under feedlot conditions. Using a structured questionnaire, 182 smallholder farmers were interviewed to determine socio-economic factors affecting their perceptions of impacts of climate change on beef production, and to identify potential protein sources they may use during drought periods in Malawi. All farmers were aware of the impacts of climate change on beef production including knowledge around the causes of deterioration of grazing rangelands, which culminated in poor animal reproduction and production performances. Perceptions of farmers were influenced more by the biophysical factors such as agroecological zone than socio-economic factors (P<0.05) indicating sensitivity of some areas to climate change in Malawi. Farmers had limited options to minimise the impacts of climate change on beef production including use of intake bulls to promote growth and increasing grazing hours. The indigenous oil-seeds and browse legume trees that farmers considered as potential protein supplements in the dry season included: Adansonia digitata (Baobab, 15% of respondents) seeds, Dolichos kilimandscharicus (wild lupin, 21%) and Vachellia polyacantha (White thorn tree) leaves 2%). Chemical composition and in vitro ruminal digestibility values of these potential rangeland-based protein sources were evaluated across two growing seasons: 2015 and 2016 and where applicable, compared to Glycine max (soybean) as a standard protein supplement. Regardless of season, soybean had the highest content of crude protein (CP) and starch followed by baobab seed (P<0.05). Crude fat content of baobab seed irrespective of season superseded all the assayed protein sources (P<0.05). The neutral detergent fibre (NDF) content was only affected by species (P<0.05), with soybean and baobab seed meals having the lowest NDF contents (P<0.05). Overall, leaves of V. polyacantha had the highest total phenols, tannins, calcium, iron and lowest in vitro NDF digestibility compared to other species across seasons (P<0.05). The largest content of phosphorus, copper and zinc was recorded in baobab seed collected regardless of season (P<0.05). Regardless of season, soybean meal had the highest content for most amino acids followed by baobab seeds, with V. polyacantha having the lowest contents (P < 0.05)Overall, irrespective of the season baobab seed had a better mineral profile and similar contents of CP, starch, NDF and amino acids compared to soybean. The effects of A. digitata seed and V. polyacantha leaf-meal on in vivo nutrient digestibility and microbial nitrogen supply, and growth performance, carcass and meat quality attributes were evaluated using Malawi Zebu steers. Three diets made up of rangeland hay and maize bran with either baobab seed meal, V. polyacantha leaf-meal or soybean meal (control) as protein source, respectively, were randomly allocated to 30 individually housed Malawi Zebu steers (182±21.4 kg and 29 months old) for 120 days. Feed offered and refused were measured daily and live weight of the steers were obtained every four weeks. Apparent in vivo nutrient digestibility was estimated usingn faecal grab samples which were collected over four days and in vitro indigestible neutral detergent fibre was used as an internal indicator. The rumen fluid was donated by a fistulated Malawi Zebu cow. Microbial nitrogen supply was calculated based on urinary purine derivative concentration of spot urine samples. On day 120, all steers were slaughtered and carcass measurements were recorded. The M. longissimus thoracic et lumborum (LTL) of each animal was sampled for meat quality measurements. Steers fed diets containing soybean and baobab seed meal had similar apparent total tract digestibility, DMI and ADG (P<0.05). However, steers fed baobab seed meal had the highest rumen microbial nitrogen supply followed by Soybean- and Vachellia-fed steers (P<0.05). Steers fed the diet containing baobab had the highest gross margins followed by steers fed V. polyacantha leaf-meal and soybean meal, in that order (P<0.05). Carcasses from Malawi Zebu steers fed baobab and Vachellia diets had higher ultimate pH than those animals fed the soybean diet (P<0.05). Muscle colour from animals fed the Soybean diet was brighter than that from animals on the baobab and Vachellia diets. During a 7-day retail display, Vachellia diet produced beef muscle with the highest resistance to browning (lowest hue angle values; P<0.05). Steers on baobab and Vachellia diets had muscles with higher (P<0.05) water holding capacity than those on soybean diet. Baobab-fed steers had muscle with the highest zinc and manganese contents compared to the other treatments. Overall, feeding steers with rangeland-based protein sources, especially baobab seed diet improved beef production and quality of Malawi Zebu steers. Although incorporation of V. polyacantha leaf-meal improved meat quality attributes, its inclusion should be minimal because of its adverse effects on animal performance. Data from the feeding trial, dry matter intake (DMI) and average daily gain (ADG) of the steers, was fitted into the two nutritional models to aid their predictions. The models used were the Beef Cattle Nutrient Requirements Model (BCNRM) and Large Ruminant Nutrition System (LRNS). The BCNRM was more accurate and precise in predicting the DMI (r2=0.95; mean bias, MB=2.5%; mean square prediction error, MSPE=0.16; and concordant correlation coefficient, CCC=0.96) than the LRNS (r2 =0.79; MB=11%; MSPE=0.19; CCC=0.82). Similarly, BCNRM was more accurate and precise in forecasting ADG (r2=0.87; MB=10%; MSPE=0.029; CCC=0.75) than LRNS (r2=68; MB=24%; MSPE=0.038; CCC=0.33). Overall, the BCNRM was more accurate and precise than the LNRS model in predicting DMI and ADG of Malawi Zebu steers fed rangeland based diets under feedlot conditions. To enhance adoption of strategies aimed at equipping smallholder beef producers to deal with climate change related feed shortages, it could be important to realign carcass classification and grading systems to suit smallholder beef production associated with rangeland-finished indigenous cattle breeds. Current beef carcass classification and grading systems in selected Southern African countries do not appropriately reward smallholder beef production associated with rangeland-finished indigenous cattle. Supportive policies and regulations have been recommended to promote value addition of rangeland-finished indigenous cattle breeds in the smallholder areas of Malawi.
Black Soldier Fly (Hermetia illucens) larvae as an alternative ingredient in processed meat
(Stellenbosch : Stellenbosch University, 2021-03) Bessa, Leah Wilson; Hoffman, Louwrens C.; Pieterse, Elsje; Marais, Jeannine; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: Black soldier fly (Hermetia illucens) larvae (BSFL) (Diptera: Stratiomyidae), primarily used as an animal feed ingredient, is beginning to show promise as a sustainable ingredient for human consumption. With this growing interest in BSFL for human consumption, there are still many gaps in knowledge that need to be filled prior to advocating for its use in human food. Amongst these are the techno-functional properties of BSFL, the food safety of consuming it, the potential product applications and finally, understanding whether consumers would be willing to consume a food product containing BSFL. Black soldier fly larvae have the ability to grow on a range of feeds, although the feed substrate and post-harvest processing (i.e., blanching) has shown to influence factors such as the nutritional profile of BSFL. This variability in BSFL composition can potentially influence its functionality for its intended end use. With the global push for sustainable meat alternatives, BSFL have the potential to be a functional and safe alternative to meat, although more research is required to validate this. To date, there is limited research on using BSFL as a meat alternative. Black soldier fly larvae grown on three different feeds (broiler-based feed, brewers’ grain, mixed cereal grain), harvested at three different ages (day 5, 8, 11), and killed using two different methods (blanching, freezing) were analysed to determine their physiochemical properties (proximate composition, pH, colour), techno-functional properties (water absorption capacity, lipid absorption capacity, emulsion capacity, emulsion stability, gel formation) and food safety (microbial content, heavy metal contamination, allergen detection). The BSFL were then incorporated into a burger patty to determine whether it could fully/partially replace meat, and a consumer survey was distributed to determine how consumers (students) would respond to the burger patties containing BSFL. The findings indicated feed, age and killing method had a significant influence on the physical composition, techno-functional properties, and proximate composition of the larvae (with the exception of chitin and ash, which was not affected by killing method). The feed and killing method were also found to influence the presence of microbes and heavy metals in BSFL, and blanching was found to increase the relative abundance of cross-reactive allergens, tropomyosin, and arginine kinase. Black soldier fly larvae grown on spent grain (11-days old) were included in beef patties at various inclusion levels, namely 0% (control), 25%, 50%, 75% and 100%, and were found to be able to replace meat only partially in a burger patty, with 25% replacement being the closest to a beef patty. Consumers preferred the appearance of the cooked BSFL patties over the raw beef patties, however, they preferred the raw beef patties to the raw BSFL patties. Factors such as gender, education level and prior experience of eating insects influenced the participants liking of the burger patties’ images. This study’s findings provide a baseline for using BSFL as a meat alternative, whilst considering the potential influences that farming, rearing, and pre-processing may have on the functionality and safety of BSFL.
Colouring the grey areas of insect mass-production to solidify their use as feed, food and biological control agents
(Stellenbosch : Stellenbosch University, 2019-12) Woods, Michael Josias; Pieterse, Elsje; Hoffman, Louwrens Christiaan; Conlong, Desmond Edward; Goosen, Neil Jurgens; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
ENGLISH ABSTRACT: The mass-production of various insect species for biocontrol methods and as feed and food is becoming common practice and several different rearing facilities have been established across the world. Although insect mass-production facilities have been set in place, the mass- production of insects is still in an infantile stage and research is necessary to optimise these systems. As with conventional intensive livestock production the success of these systems, as well as the costs implicated, can largely be contributed to the nutrition of the animals. Trials were conducted to try and establish the nutrient requirements of selected insect species based on the body composition technique, a method commonly used for conventional livestock. Positive results were obtained for all involved insect species and led to an increase in production output, as well as to a decrease in the cost of production. For mass-produced insects to reach their full potential they need to be tailored for their end use. A study was conducted where larvae were reared on a substrate rich in polyunsaturated fatty acids in attempt to manipulate the fatty acids that they deposited into their biomass, and subsequently to evaluate the effect this had on the production and meat quality parameters of the animals the larvae had been fed to. Promising results were observed as an increase in the omega-3 fatty acids were observed in the larval biomass and the same occurred in the meat of the quails the enriched larvae were fed to. Although, the ratio of polyunsaturated- to saturated fatty acids could not be changed. Insect processing is another field that needs attention and the fractionation of insect biomass into protein, fat and chitin can result in significant increase in the margins made both environmentally and economically. An enzymatic fractionation method was developed that resulted in the isolation of protein, fat, and chitin and greater total recoveries were obtained compared to previous studies. The subsequent quantification of the chitin content of insects has also been a problem in the past and based on chitin isolation from crustaceans, a gravimetrical protocol was developed to address this issue. The resulting protocol led to the most repeatable and accurate estimation of the chitin content of insect larvae to date. Overall, the results obtained from the series of studies were a step in the right direction to solidify the mass-production of insects for biocontrol methods as well as for feed and food purposes.
Comparing feed use efficiency and enteric gas production of Holstein and Jersey cows in a kikuyu pasture-based system using mathematical models
(Stellenbosch : Stellenbosch University, 2020-03) Bangani, Noluvuyo Muriel; Dzama, Kennedy; Muller, C. J. C.; Cruywagen, C. W.; Nherera-Chokuda, F.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
ENGLISH ABSTRACT: Feed use efficiency to synthesise maximum amounts of milk while ensuring responsible use and protection of the environment is of significance for sustainable milk production. The aim of this study was to compare factors affecting milk production, nutrient use and enteric gas production efficiencies of Holstein and Jersey cows that were reared under similar environmental conditions and management practices. Data used were lactation records of 122 Holstein and 99 Jersey cows, collected from 2005 to 2014. Records included cow birth date, calving date, lactation number, body weight (BW), kg milk yield (MY), % fat (MF) and % protein (Mprot). Cows were reared as one herd on kikuyu pasture and received on an as-fed basis 7 kg of concentrate containing 17% crude protein (CP) per day, fed in two equal portions after each milking. The total dry matter intake (DMI) was estimated using the National Research Council (NRC, 2001) method. Pasture intake was calculated as the difference between DMI and concentrate dry matter intake. The mean DMI, MY, kg MF and kg Mprot were higher in Holsteins while Jerseys had higher %MF and %Mprot. Jersey MY was 74% but when corrected to energy corrected milk (ECM), 85% that of Holsteins. Milk increase from primiparous to mature cows (parity ≥4) was 26.5% in Holsteins and 23.7% in Jerseys. Age at first calving (AFC) did not differ between breeds. The calving season (CS) did not affect mean test-date MY but cows that calved in summer had a flatter lactation curve. Mean lactation number was lower and the inter-calving period (ICP) longer in Holsteins than Jerseys. Cows with the ICP below 13 months tended to produce on average less 305-day milk yield. Jersey cows showed higher efficiency in DMI/kg BW, MF/kg DMI, Mprot/kg DMI, ECM/kg DMI, ECM/kg BW and MY/100 kg BW. Holsteins were efficient in MY/kg DMI. Both breeds were in negative energy balance (NEB) during the transition and early lactation stages, with Holsteins having longer and more intense NEB. The net energy intake (NEI)/kg ECM, NEI/kg metabolic BW (BW0.75) and net energy for maintenance (NEm)/kg BW0.75 were higher in Holsteins compared to Jerseys. However, after accounting for NEm, (NEI-NEm)/ECM, Holsteins had higher gross energy efficiency. Milk nitrogen (MN)/nitrogen intake (NI) was higher in Jerseys compared to Holsteins. The NI/kg BW0.75 did not differ between breeds. Jerseys had higher faecal nitrogen (FN)/100 g NI but lower urinary nitrogen (UN)/100 g NI, protein requirements for scurf losses (SPA) and therefore lower manure nitrogen (ManN)/kg NI than Holsteins. Holsteins produced more kg carbon dioxide (CO2)/day, but low CO2/kg DMI and CO2/100 kg BW than Jerseys. Breeds did not differ in CO2/kg ECM. Holsteins emitted less methane (CH4) g/kg DMI and CH4/100 kg BW, while Jersey emitted less CH4/kg ECM. Mature cows produced on average 16% more CH4 than their primiparous counterparts. With lactation stages, the highest CH4 emissions were observed during mid-lactation with cows producing on average 28% more daily CH4 when compared to the transition period. This indicates that accounting for production stages in estimating the methane emission factor (MEF, CH4/head/year) will bring more accuracy and can therefore be recommended for regional and national inventories for SA dairy breeds. From this study, it can be concluded that neither of the breeds were overall more efficient regarding all traits, but Jersey cows showed higher efficiency in most measured traits.
Comparing the effects of tranquilisation with long-acting neuroleptics on blue wildebeest (Connochaetes taurinus) behaviour and physiology
(Stellenbosch : Stellenbosch University, 2015-12) Laubscher, Liesel L.; Hoffman, Louwrens C.; Pitts, Neville I.; Raath, Jacobus P.; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: In South Africa, large numbers of game animals are translocated annually. These animals are subjected to a great amount of stress and the use of long-acting neuroleptics (LANs) has become a common practice to minimize animal stress. Long-acting neuroleptics suppress behavioural responses without affecting spinal and other reflexes, and can be administered in such a manner that a single dose results in a therapeutically effective tissue concentration for anywhere between three to seven days. The mammalian stress response consists of a variety of physiological responses, and the study aimed to quantify a number of these responses in blue wildebeest (Connochaetes taurinus). This was done in order to compare the effects of a commonly used LAN, Acuphase® (zuclopenthixol acetate in vegetable oil), with a newly developed LAN, Acunil® (zuclopenthixol acetate in a low-release polymer), in minimizing the stress response of blue wildebeest in captivity. A human biotelemetry belt, Equivital™ EQ02, was modified to fit this species, and the results from a validation study indicated that the belt accurately measured heart and respiration rate, respectively, in blue wildebeest. The belt also measured motion accurately, and this made the monitoring of conscious animals prior to and after being treated with a LAN, possible. A faecal glucocorticoid metabolite (FGM) assay was also validated for use in blue wildebeest. Three sets of trials were performed in which animals received one of three treatments; Acuphase®, Acunil® or a placebo in order to evaluate the effect of each. Animals were monitored for 12 hours before and 12 hours after treatment. The results showed that although both Acuphase® and Acunil® resulted in a decrease in vigilant behaviour and an increase in resting behaviour, similar results were observed when animals received a placebo. Animals treated with Acunil®, however, exhibited a decrease in explorative behaviour as well as an increase in the time they spent eating. Heart rate was unaffected by any of the three treatments, and this lack of effect by either of the LANs may potentially be due to reflex tachycardia in response to hypotension. Respiration rate was lowered by both LANs, specifically during certain behaviours, with this effect being absent in placebo-treated animals. In addition, the motion of the animals indicated that LAN-treated animals had a lowered flight response to a person entering the enclosure. Endocrine parameters measured in the blood and faeces of the animals before and after treatment revealed a minimal effect. Neither the acute nor the chronic stress response appeared to be significantly reduced by treatment with Acuphase® or Acunil®. In addition, immune function (as quantified by white blood cell count and neutrophil response) revealed that the chronic stress of captivity lowered the immune response of the animals. This decrease in immunocompetence, however, could not be ascribed to any of the LAN treatments. In conclusion, the most pronounced effects observed with the administration of both LANs included a decrease in respiration rate, and responsiveness of the animals. Long term studies on the effect of LAN administration on immune function and endocrine responses may yield more conclusive results regarding the stress responses of wild animals in captivity.
Copy number variations in South African Nguni cattle : prevalence, characterization and genetic diversity
(Stellenbosch : Stellenbosch University, 2016-12) Wang, Magretha Diane; Dzama, Kennedy; Muchadey, Farai Catherine; Rees, Jasper; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: Copy Number Variations (CNVs) comprise of deletions, duplications and insertions larger than 1kb that occur within genomes. The identification of CNVs within regions of the bovine genome important for adaptation renders them a potential role in breed formation and adaptation. South African Nguni cattle are adapted and demonstrate an enhanced ability to endure the harsh environmental conditions of Southern Africa. This study investigated the prevalence of CNVs in the genome of South African Nguni cattle. CNV occurrence and distribution within Nguni subpopulations was assessed and comparisons with other South African cattle breeds were performed. The dynamics between CNVs and haplotype blocks (HPBs), correlations amongst CNVs and the genic locality of CNVs were investigated with the objective of determining CNV prevalence in adaptation. The Illumina BovineSNP50 beadchip was used in the first experiment to genotype 492 South African Nguni cattle sampled nationwide. PennCNV software identified 334 CNV regions (CNVRs) of between 30kb and 1Mb in length. Population structure analyses was performed and HPBs identified using ADMIXTURE and PLINK software respectively. Five subpopulations were evident with some degree of CNV segregation amongst populations. CNVRs covered or lay within 10Mb of 289 genes of which 149, 28, 44, 2 and 14 genes exclusive to the five sub-populations were identified. Some degree of overlap between CNVRs and the 541 HPBs was evident. In the second experiment, 59 Nguni genotypes were analyzed using the Bovine 50K Beadchip in conjunction with six other South African breeds. PennCNV software identified 356 unique CNVRs. One hundred and sixty three CNVRs identified in more than 1 animal were utilized as genetic markers to assess within and between breed genetic diversity (GD). Between breed group GD scores were 2.510, 6.115 and 4.233 for the Sanga, Taurine and composite breeds respectively. One hundred and two (Taurine) and seven (Sanga and composite) of the CNVRs demonstrated a significant (p≤0.05) association with one another. PANTHER overrepresentation analyses demonstrated significant representation of a number of processes, functions, components and proteins by correlated CNVR genes. CNVR based phylogenetic clustered animals of the same breed group together. In the third experiment 24 Nguni animals were sequenced at 7X coverage using illumina next generation sequencing technologies. Reads were mapped to the UMD3.1 reference genome and RAPTR-SV software was utilized to identify CNVs. CNVs identifed were filtered according to the number of reads that support the event with low (F10), medium (F45) and high stringencies (F75). Adjacent and overlapping CNVs were merged to form 399, 55 and 23 unique CNVRs that covered or lay within 1Mb of 358, 51 and 23 genes at F10, F45 and F75 stringencies respectively. NGS tools identified smaller CNVs compared to those reported from SNP data. Despite discrepancies between array and NGS methods, CNVR genes represented the same specific ontologies. The study demonstrated CNVRs to be prevalent in South African Nguni cattle, with potential role in breed formation and adaptation. CNVR GD scores, population structure, distribution and incidence dynamics were thus ascertained for the South African Nguni.
The Damara sheep : an appraisal of its reproductive performance and potential
(Stellenbosch : University of Stellenbosch, 1998-03) Schoombee, Cornelius Johan Albertus; Coetzer, W. A.; Barry, D. M.; University of Stellenbosch. Faculty of Agricultural Sciences. Human and Animal Physiology.
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Determination of variance components for skin traits of ostriches in South Africa
(Stellenbosch : Stellenbosch University, 2023-03) Nemutandani, Khetho Ratshilumela; Engelbrecht, Anel ; Cloete, Schalk W. P. ; Dzama, Kennedy; Tada, Obert; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
ENGLISH ABSTRACT: In the South African ostrich industry, production of high quality leather is a necessity for sustainability and competitiveness on the world market. However, most skins are downgraded due to poor quality, constraining enterprise revenue. The aim of this study was to identify factors contributing to skin value, to determine genetic and environmental parameters for ostrich skin traits, as well as to evaluate the performance of pure and crossbred ostriches for skin traits. Skin size (SSZ), skin grade (SG) and quill value (QV) were assessed as predictors of skin value, using multiple regression techniques. Pearson’s correlations among independent variables confirmed that SG was the dominant driver of skin value, as indicated by a high negative correlation (r=-0.88) with skin income. Skin traits such as nodule size score (NSZ), nodule shape score (NS), hair follicle score (HF) and pitting score (PIT) mostly failed to reflect the variation in skin value accounted for by QV and SG, respectively. Single-trait heritability estimates, derived on South African Black (SAB) birds, for skin traits such as SSZ, skin weight (SW) and skin thickness (ST) were 0.37±0.06, 0.27±0.06 and 0.20±0.05, respectively. Overall, direct heritability ranged from low (0.08) for pitting scores to high (0.42) for hair follicle scores. Genetic correlations of slaughter weight (SLW) with SSZ, SW and ST were 0.92, 0.48, and 0.15. A positive genetic correlation of 0.33 was found between SLW and NSZ. A high genetic correlation of 0.71 existed between scores for NS and NSZ. For threshold traits, heritability estimates ranged from 0.17 for nodule direction (NDIR) to 0.47 for nodule outliers (OUTL) in the 5- trait threshold model analysis for non-linear and binomial traits. In the 6-trait linear- threshold analysis including SSZ as a linear trait, heritability estimates ranged from 0.20 for NDISTR to 0.39 for OUTL. For both sets of analyses, significant genetic correlations were found between OUTL and PIT (respectively 0.49 and 0.71). Evaluation of purebreds showed that Zimbabwean Blue (ZB) and Kenyan Red (KR) birds outperformed their SAB contemporaries for most size-related traits (P<0.05). Heterosis were found for SLW, SSZ, and NSZ, for SAB and ZB as well as for SAB and KR combinations. The effect of the taller KR dam line was significant for SLW, neckline total length, neckline crown length and neckline width in the middle. However, most of the size dependent genetic group effects were reduced or removed when farm weight was modelled as a covariate across analyses. High scores for HF were observed for all the crosses though. It was concluded that: 1. Skin grading was the dominant force in determining skin value; 2. Genetic variation existed and exploitable levels of variation were found in most quantitative skin characteristics; therefore genetic progress appear feasible through selection; 3. Genetic progress can also be achieved for traits not conforming to the assumptions of normality; 4. ZB and KR birds performed better for size-related traits than their SAB contemporaries, indicating that commercial crossbreeding could improve slaughter weight and size-related traits in hybrids. Overall, this study provides information to the ostrich industry regarding options for the exploitation of additive genetic gains, the choice of breeds, as well as crossbreeding options. This information will provide a sound foundation for genetic improvement of skin traits that is based on scientific principles.
Development of a cost-effective system for ovoviviparous production of Artemia nauplii at low-salinity as live food for the larvae of the African catfish (Clarias gariepinus: Burchell, 1822)
(Stellenbosch : Stellenbosch University, 2019-04) Bwala, Richard; Salie, Khalid; Van Stappen, Gilbert; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: The brine shrimp Artemiais a small crustacean used as live food in fish and shell fish culture. Among other live food types which are commonly used in aquaculture, Artemia is widely known and accepted mainly due to the ease with which it can be used in hatcheries either in the form of nauplii, hatched from cysts, or as decapsulated cysts which are sold as off-the-shelf products. Supply of cysts has been hampered due to discontinuity of Artemia distribution in natural biotopes, meteorological fluctuations, climatological changes and possible overharvesting of resources. This has led to instability and resulted in fluctuations and sometimes reduction ofthe global production. Hence regional cyst supply has been insured in many places through artificial inoculation and man-managed production in salt ponds. Hatcheries in sub-Saharan Africa have so far relied on importation of product of variable quality, thereby adversely affecting fish production efficiency and reducing the competitiveness of aquaculture in this region. This research work contributes to the knowledge on the alternative ways for the supply of Artemia as live food for use in hatcheries. Firstly, literature was reviewed focusing on the general overview of the status of aquaculture globally and within the sub-Saharan region of Africa; the taxonomy, biology, culture and applications of Artemia; on the taxonomy, biology and aquaculture production of the African catfish Clarias gariepinus, and the requirement of live food for their larvae. Among other challenges which aquaculture faces in Africa, a common re-occurring factor identified is the insufficiency or non-availability of fish seed which in turn has been partly associated to the scarcity of live food which is an essential component in the hatchery production of the larvae of many cultured fish species. Secondly, data are presented on a study of low salinity (0 – 32 g L-1) culture of Artemia using four strains from two bisexual [Great Salt Lake (GSL), Vinh Chau (VC)] and two parthenogenetic [Tuz (TUZ), Balikun (BLK)] populations. Laboratory tests were performed, firstly, to measure axenically the survival of instar I and II at low salinity during a 48 h period. The use of the two instars was based on the hypothesis that ambient salinity does not affect the embryo and instar I nauplii of Artemia, and to assess if using instar II nauplii to inoculate culture would affect survival. Similarly, survival of the Artemia at two inoculation ages (i.e. nauplii and pre-adult) was tested xenically over a nine days period at these low salinities. The two inoculation ages were used based on the hypothesis that mortality rate usually reduces as Artemia attains maturity. Results of both tests showed that the low salinity influenced survival with respect to the strain types. With respect to the two instar developmental stages, no difference was observed as a result of the low salinities tested. With regard to the inoculation ages, no differences were also observed among the salinities tested, except atlower (5 g L-1) salinity where the lowest survival was recorded. Furthermore, a test on the effect of low salinity on the reproductive and life traits showed that both salinity and strain had an influence on the parameters measured. Generally, high survival was observed at those low salinities where survival occurred, but the highest was recorded at 20 and 32 g L-1 (control) salinity. Overall the best performance in terms of the reproductive and life traits measured was observed with the Great Salt Lake (GSL) strain. In particular, the GSL strain had the highest total offspring as well as the number of offspring produced as nauplii. We conclude that 20 g L-1 salinity and the GSL strain are the most suitable for use in mass culture. Subsequently, this research work also presents a study assessing the effect of five locally sourced agricultural based materials (Oat pellet, canola pellet, barley pellet, whole barley grain, whole wheat grain) as sole diet on growth and survival, and their suitability for maintaining a reproducing population of GSL Artemia franciscana at low (20 g L-1) salinity. Two separate tests were conducted which involved firstly a nine days small scale (using 500 mL glass bottles) feeding experiment in order to screen and select suitable feed material(s), followed by up-scaling and a mass culture of Artemia from the nauplii stage and through the reproductive stage (43 days), using the selected feed material(s). Both the screening and the up-scaled biomass tests showed that feed type influences the growth and survival of the animals, whereby feeding a stock suspension prepared from barley pellet resulted in better performance than feeding with the other feed materials. The up-scaled biomass test confirmed that the barley pellet diet could be used for the culture of actively reproducing biomass of the GSL strain of Artemia franciscana. During the reproductive period of the biomass daily nauplii harvest was achieved over a period of 22 days, after which the culture was terminated when nauplii production reduced consistently. Despite low levels of nutrients of the different feed materials, the adults fed with the test feed and the nauplii produced ovoviviparously were found to contain appreciable levels of protein, essential and non-essential amino acids as well as saturated, mono-unsaturated and poly-unsaturated fatty acids in their tissues. In order to achieve higher nauplii production, however, feed manipulation, contrary to feeding with sole diets may yield better results. The suitability of the ovoviviparously produced nauplii was tested by feeding them directly to catfish Clarias gariepinus larvae in comparison with oviparously produced nauplii and decapsulated cysts. Higher survival, better protein efficiency ratio and food conversion ratio were observed in catfish larvae fed with the ovoviviparous nauplii. We conclude that the ovoviviparous nauplii could serve as an alternative live food for larval fish. The economic viability of using the ovoviviparously produced nauplii at the current production capacity of the developed pilot system versus the use of the imported Artemia cysts was analyzed. Cost analysis of producing an individual C. gariepinus larva fed with the ovoviviparously produced Artemia nauplii was found to be 2.15 USD while the cost involved to produce the fish larva fed with locally shopped imported decapsulated Artemia cysts was approximately 0.002 USD. The result of the analysis clearly shows that at the current capacity of the developed nauplii production system, the cost of feeding anindividual C. gariepinus larva is far higher than when the imported decapsulated cysts are utilized. However, there is still a lot of room for optimisation of many aspects of our production system, so that the result of the above comparison may be altered in favour of the use of ovoviviparous nauplii. Moreover, the overall benefits of using the ovoviviparous nauplii should not only be anchored on monetary terms but also on the associated benefits such as fish larval growth, survival rate and postlarval quality, constant and predictable quality of the live food offered to the fish larvae, self-reliance of live food production etc. Finally, the overall results of this work are discussed in the framework of its objectives. Some limitations and their implications, which may have interfered with validity of the results, are highlighted. In order to enhance production of the nauplii, it is recommended for the system to be optimized and more studies to be conducted on various aspects such as stocking density of the culture, the extent to which the feed types offered affect the performance of the maternal population in terms of fecundity and type of reproduction, and the nutritional quality of the ovoviviparous nauplii.
Development of a livestock management database system towards sustainable smallholder farming systems in South Africa
(Stellenbosch : Stellenbosch University, 2022-04) Mapiye, Obvious; Molotsi, Annelin H.; Makombe, Godswill; Dzama, Kennedy; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: The commercialisation of smallholder farmers has taken the lead on the development agenda of many developing countries. Invariably, the majority of smallholder livestock producers are less productive than commercial producers and lag in commercialisation. Apart from the multifaceted challenges that smallholder farmers face, limited access to appropriate information and extension services constrains their sustainability. Therefore, the aim of this study was to design and develop a Livestock Management Database System (LMDS) for improving the sustainability of commercially oriented smallholder cattle producers in the North West Province of South Africa. The system promotes the efficiency of delivering agricultural extension services and the upscaling of smallholder livestock production through improved access to tailored information and services. The study was guided by the pragmatic paradigm, which accommodates positivism (quantitative) and normative (qualitative) perspectives. A partially mixed sequential explanatory design with a dominant quantitative method was adopted. A structured questionnaire was administered to 101 commercially oriented beneficiaries of the Nguni cattle project in North West Province, South Africa, to collect quantitative data. Qualitative data were collected through focus group discussions (FGDs) and key informant interviews (KIIs) with farmers and extension officers, respectively. A double-bounded contingent evaluation method was used to estimate the farmers’ willingness to pay (WTP) for rangeland conservation and regeneration. A binary logistic regression model was used to evaluate the determinants of farmers’ WTP. The results show that most farmers (>80%) were willing to pay the initial bid price of ZAR165.00, with the estimated mean WTP being ZAR244.00 ha -1 year -1 for improving rangelands. The logistic regression findings show that the farmers' WTP responses were influenced by education (p = 0.012), most important breed (p = 0.039), farming experience (p = 0.026), goat ownership (p = 0.022), ecoregion (p = 0.079), and income from cattle sales (p = 0.048). The high WTP results highlight the potential of involving the smallholder cattle farmers in implementing payment-based programs designed to improve the ecological sustainability of rangeland ecosystems and even introduce new interventions such as the LMDS. However, one of the complex challenges of driving the growth of commercially oriented smallholder farmers is ensuring that farmers understand and use new technologies. Thus, explaining their behavioural intentions before technology development is one of the most effective ways to increase adoption and identify potential design issues. Therefore, the study investigated the farmers’ experiences of using ICTs and their perceptions of the usefulness of the LMDS in livestock production. Results revealed that over 75% of the farmers had smartphones and smartphone operating skills, and nearly two-thirds were using the internet to search for agricultural information. About 80% had a strong positive perception of the usefulness of the proposed LMDS towards their livestock production. FGDS and KII results also observed higher positive perceptions towards the innovation. The Chi-square statistic was used to test the association between farmers' socioeconomic characteristics and perceptions of the usefulness of the LMDS. The results show that education level, smartphone ownership, farming experience, cattle herd size and gender influenced farmers’ perceptions of the LMDS. Poor mobile network connectivity (44%) and lack of digital skills (20%) were the limitations perceived to hamper the adoption of the innovation. The deeper insights from study findings on the perceived usefulness of mobile technology can be beneficial to policymakers, researchers, and development agents and institutions when developing interventions for adoption by farmers. The LMDS development process involved a human-centred design thinking process in which development activities were based on the farmers and extension officers’ needs and expectations. Development of the LMDS has reached the prototyping phase, which involves software development and validation in the actual operational environment.
Development of an artisanal cheese making model for small-scale farmers in South Africa
(Stellenbosch : Stellenbosch University, 2020-03) Nyamakwere, Faith; Raffrenato, Emiliano; Esposito, Giulia; Dzama, Kennedy; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
ENGLISH ABSTRACT: The aim of the current study was to develop an artisanal cheese-making model for small-scale dairy farmers in South Africa. Firstly, a comprehensive survey was conducted to characterize cheese (n=40) from the small-scale producers (n=15) in the Western Cape Province, South Africa. The results indicated that the cheese market was diverse, with majority in the “Other” group (47.5%) followed by Cheddar (32.5%) and then Gouda (20.0%). Most of the cheese (45%) was aged for three months and produced using pasteurized milk. The second objective evaluated the feasibility of on-farm artisanal cheese-making. Pecorino and ricotta cheese-making trials were setup at Welgewallen experimental farm of Stellenbosch University and step by step protocols were developed after testing all equipment and ingredients. It was recommended to use moulds or ricotta baskets with big holes, sharp curd cutter, cut curds to cubes of 1–2 cm3 and further test raw milk. The effects of breed [i.e. Holstein-Friesian (HF), Jersey and crossbreds (HF x Jersey)] on cheese physicochemical and microbiological properties were investigated. Pecorino-style cheese was processed at four farms with two batches for each respective breed in summer of 2018 and aged for 60-days. The Jersey milk had higher casein proportions resulting in higher yields with more yellow cheese than others (P < 0.05). Cheese physicochemical properties were noted to significantly change during aging and the Jersey cheese had higher (P < 0.05) protein and fat content at day 60. Crossbred cows had cheese with higher (P < 0.05) hardness and chewiness values. These results will help farms when selecting dairy breeds. Cheese quality can be influenced by the aging conditions, therefore, the effect of different aging conditions (commercial and artisanal) on cheese physicochemical and microbial properties were investigated. The cheese was aged for 60 days and samples collected at day one, 30 and 60. The artisanal chamber used a domestic humidifier and air conditioner to control humidity and temperature, respectively. The artisanal chamber was found to be affordable and yielded good quality cheese. The microbiological quality of the cheese from both the survey and cheese making trials highlighted the importance of implementing effective methods to control bacteria, therefore, the efficacy of gamma irradiation against Listeria monocytogenes, Escherichia coli, coliforms and aerobic colony counts on cheese and its effects on physicochemical properties were assessed. Some physicochemical properties were reduced (P < 0.05) by the irradiation treatment but were within the expected ranges for hard cheese. The irradiation treatment was found to be an ideal affordable method to control food pathogens for small-scale producers. The last objective assessed the benefits, challenges and production costs for artisanal cheese making. The calculated value for the initial investment in terms of equipment was R23 669.17. Cheese making was noted to give higher profit margins compared to selling raw milk. However, one of the major challenges identified includes lack of knowledge in terms of processing techniques and economic information. This study demonstrated that cheese can be processed at a small-scale with lower capital investment in equipment and ingredients.
The effect of inoculants on silage fermentation properties and on animal production
(Stellenbosch : University of Stellenbosch, 2000-12) Meeske, Robin; Cruywagen, C. W.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Animal Sciences; Jacobs, Ivan
ENGLISH ABSTRACT: Maize, forage sorghum, lucerne, oats, barley and triticale are the most common silage crops in South Africa, while tropical grasses like Eragrostis curvula and Digitaria eriantha are ensiled to a lesser extent. The aim of this study was to determine the effect of adding a lactic acid bacterial inoculant to E. curvula, D. eriantha, lucerne, forage sorghum, maize and oat silage. The effect of the addition of a lactic acid bacterial inoculant when ensiling E. curvula on the fermentation dynamics during ensiling and the aerobic stability of the silage was determined. The addition of the lactic acid bacterial inoculant to E. curvula at ensiling resulted in a more rapid lowering in pH and improved preservation. Inoculated silage had a higher lactic acid content, less protein breakdown and a lower butyric acid content compared to that of the control silage. Both silages were stable when exposed to air for five days. Digitaria eriantha was ensiled, with or without the addition of a lactic acid bacterial inoculant containing Lactobacillus plantarum. Streptococcus faecium and Pediococcus acidilactici together with the enzymes, cellulase, hemicellulase and amylase. The addition of the inoculant resulted in a more rapid drop in pH, a higher level of lactic acid, an increase in the number of lactic acid bacteria, less protein breakdown and lower numbers of enterobacteria, clostridial spores, yeast and mould compared to the control silage. Digitaria eriantha hay, control and inoculated silage diets were fed to 24 Merino rams (n = 8 per treatment) to determine intake and digestibility. The intake of diets consisting of 90.9% D. eriantha hay, control silage or inoculated silage, differed significantly (p<0.05) at 1395, 1540 and 1848 g DM/day, respectively. The in vivo organic matter digestibility (glkg) of D. eriantha hay, untreated silage and inoculated silage diets was 561, 546, 574, respectively. The addition of the bacterial inoculant when ensiling D.eriantha resulted in better preservation, improved aerobic stability, as well as a higher in vivo organic matter digestibility and intake of D. eriantha silage. The addition of an inoculant or molasses to lucerne (Medicago sativa), ensiled in laboratory silos was investigated. The addition of the additives resulted in an increased preservation rate as indicated by a more rapid lowering of pH, a faster rate of lactic acid production and less protein breakdown compared to control silage. The inoculant was more effective than the molasses in improving the rate of preservation. The aerobic stability of lucerne silage was not affected by inoculation or the addition of molasses. The addition of an inoculant to wilted big bale lucerne silage was studied. The inoculant improved silage quality as indicated by a lower pH, higher lactic acid content, lower ammonia nitrogen content and lower level of butyric acid in inoculated silage compared to the control lucerne silage. The composition of big round bale lucerne silage differed markedly from that of lucerne ensiled in laboratory silos as the former had a higher pH, ammonia nitrogen, butyric acid and acetic acid content and a lower lactic content. Whole crop forage sorghum cultivar FS2 was harvested at the late bloom (20.7% DM) and soft dough (28.9% DM) stages of maturity and ensiled in laboratory silos with the addition of commercial silage inoculants. At both stages of maturity the inoculants caused a more rapid rate of pH decline and a higher amount of lactic acid production. All the silages were well preserved. Silages of the sorghum ensiled at the late bloom stage with all treatments were stable after 5 days of aerobic exposure, whereas sorghum ensiled at the soft dough stage with the addition of the inoculants deteriorated upon aerobic exposure. It is concluded that addition of lactic acid bacterial inoculants to mature sorghum at ensiling might impair the aerobic stability of the silage. The yield, nutritional value and production potential of silage made from twenty one maize hybrids was compared. It was concluded that maize hybrids did differ in metabolizable energy content, rate of digestion, predicted intake and predicted milk production potential. The content of NDF and ADF did not differ between the maize hybrids used in this study and could therefore not be used to predict nutritional value or production potential. Maize was harvested at the hard dough stage and ensiled with or without the addition of a lactic acid bacterial inoculant in laboratory silos and in 210 litre drums. The adding of the inoculant to maize at ensiling did not result in a more rapid drop in pH and higher levels of lactic acid. The intake and growth of South African Mutton Merino lambs fed inoculated and untreated maize silage diets was determined. The average daily gain of lambs fed a diet consisting of either 60% control or inoculated maize silage over a growth period of 60 days was 239 ± 26 and 255 ± 44 g/day, respectively. Although the laboratory study showed very little effect of adding a lactic acid bacterial inoculant to maize at ensiling, lambs tended to consume more of the inoculated silage. In the second study the effect of the addition of a lactic acid bacterial inoculant with an enzyme to maize at ensiling on the fermentation dynamics during ensiling, aerobic stability of the silage, the intake, milk production and milk composition of Jersey cows fed maize silage diets was determined. The inoculant did not result in a more rapid lowering of the pH or a more rapid lactic acid production compared to untreated maize silage made in laboratory silos. Both the control and inoculated maize silages were well preserved. The addition of the inoculant to maize at ensiling improved the palatability, intake and the aerobic stability of maize silage compared to the untreated control maize silage. Milk production, milk composition, live weight and condition score of Jersey cows was not significantly affected by the addition of the inoculant to maize silage. The effect of the addition of an enzyme containing lactic acid bacterial inoculant to big bale oat (Avena sativa, cv Cederberg) silage on silage composition, silage intake, milk production and milk composition of Jersey cows was determined. The crop was cut at the bloom stage, wilted and ensiled in big round bales. The inoculant, Sil-All, was applied during the baling process on half of the bales. Silages were fed to Jersey cows in an intake and milk production study. Both the control and inoculated oat silages were well preserved. The inoculated oat silage had a lower level of butyric acid than the control oat silage. Cows fed the inoculated oat silage produced more (P=O.05) milk (17.7 kg/day) than cows fed the control oat silage (16.7 kg/day). The addition of a lactic acid bacterial inoculant to big bale oat silage improved silage composition and animal performance. This study clearly showed that the composition of silages made in bunker silos under commercial farm conditions differ largely from that of silages made in small scale laboratory silos. When the effect of silage additives on aerobic stability of silage is determined the evaluation should include studies on large scale bunker silages. Evaluation of silage additives should include intake and animal production studies.
The effect of maize vitreousness and a starch binder on in vitro fermentation parameters and starch digestibility in dairy cows
(Stellenbosch : Stellenbosch University, 2017-12) Van Zyl, Johan Hendrik Combrink; Cruywagen, C. W.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: Maize kernels consist of hard vitreous endosperm and soft floury endosperm, and the ratio of the vitreous to floury endosperm determines the vitreousness of the kernel. As ruminal fermentation and animal performance are higher for low vitreous maize, lower vitreous maize is favoured for inclusion in animal feeds. Very high ruminal starch degradability may, however, lead to metabolic disorder risks such as acidosis. The objective of this study was to evaluate various techniques for routine analysis to determine a rapid, simple, inexpensive method to predict maize vitreousness accurately. Secondly, the usability of Near-infrared spectroscopy (NIR) technology in the anmal feed industry to predict the fractional rate and extent of ruminal starch degradability in maize differing in vitreousness was investigated by means of in vitro starch disappearance. Thirdly, the effect of the treatment of maize with a commercial starch binder on rumen kinetics of lactating dairy cows was investigated by means of in vitro gas production and in vitro starch disappearance studies. For this part of the study, it was attempted to bind some of the maize starch (1 mm grind) in vitro with the treatment of a commercial starch binder. The fourth objective was to investigate the effect of particle size (1mm vs 4 mm grind) and a starch binder on in vitro disappearance of starch in low vitreous maize. The final objective was to determine the effect of starch binder treatment of low vitreous maize on the apparent total tract digestibility and production responses in lactating dairy cows. Ninety maize samples of different vitreousness were collected and subjected to NIR at a single absorbance of 2230 nm and PSI trough a single 106 μm screen. Samples were subsequently ranked according to vitreousness. The ten hardest and ten softest samples were selected to evaluate NIR, particle size index (PSI), and Rapid visco analyzer (RVA) rheological analyses as potential methods for the determination of maize vitreousness against X-ray micro-computed tomography (XCT). Significant relationships were found between NIR and PSI regarding hardness predictions, while the study with the smaller sample set (n = 10) showed significant relationships between PSI, NIR, RVA peak time (corresponding time required for a sample subjected to rheological analysis to reach peak viscosity) and RVA peak viscosity (the process of gelatinization and occurs at the equilibrium point between swelling and polymer leaching) in relation to XCT regarding maize vitreousness determination. All other rheological information data were not accurate to predict maize hardness. As NIR technology is already available and meets the requirements of speed, simplicity and inexpensiveness, it was concluded that NIR at a single absorbance of 2230 nm is the most accurate and practical method to determine maize vitreousness in the animal feed industry. Thereafter, six maize samples of decreasing vitreousness were selected from ninety samples with known vitreousness and subjected to in vitro starch disappearance at 0, 3, 6, 12, 24 and 48 h of incubation. The subsequently determined fractional rate of disappearance and predicted ruminal starch disappearance decreased significantly as maize vitreousness increased. Hardness indexes calculated from NIR analyses at a single absorbance of 2230 nm showed inverse linear and quadratic relationships for both fractional rate and extent of starch disappearance. It was concluded that NIR technology could be used to predict fractional rate and extent of starch disappearance from the rumen based on maize vitreousness. In a further study one low and one high vitreous maize sample were selected from the ninety samples with known vitreousness. Both samples were treated with equal amounts of a commercial starch binder (Bioprotect) and distilled water to determine the effect of the treatment on in vitro gas production and in vitro starch disappearance. The rate of in vitro gas produced from low vitreous maize was higher than that of high vitreous maize, irrespective of treatment. All other in vitro gas production parameters did not differ between treatments. In vitro starch disappearance values at 6, 12 and 24 h time intervals were, irrespective of binder treatment, higher with low vitreous maize compared to high vitreous maize. Starch binder treatment, however, did not affect in vitro starch disappearance. In a further in vitro study, maize samples of known low vitreousness were milled through 1 mm and 4 mm sieves, respectively. The milled samples were then thereafter treated with equal amounts of a starch binder (Bioprotect) and distilled water to determine the effect of particle size and treatment on in vitro starch disappearance after 0, 3, 6, 12, 24 and 48 h of incubation. Particle size reduction increased (P < 0.05) both fractional rate and extent of starch disappearance, while binder treatment showed a tendency (P < 0.10) towards decreased fractional rate and extent of starch disappearance. Despite no differences in ruminal kinetics with the binder treatment of 1 mm milled maize, treatment of 0.4 mm milled maize, however, indicated lower (P < 0.05) fractional rate and extent of starch disappearance. It was concluded that a reduction in particle size of maize with hammer mill processing changes rumen starch fermentation characteristics and that the treatment of 4 mm milled maize with a commercial starch binder may alter rumen fermentation kinetics. In the final trial, six primiparous Holstein dairy cows were used to investigate the effect of a starch binder (Bioprotect) treatment of low vitreous maize on total tract nutrient digestibility and production parameters of lactating dairy cows. Starch binder (10/L/tonne grain) or water treated maize were used in two TMR’s. No differences in dry matter intake, milk yield, 4% fat corrected milk yield, energy corrected milk yield, milk fat concentration, milk fat yield, milk protein concentration, milk protein yield, milk urea nitrogen concentration or somatic cell count were found between binder treated or water treated maize. Apparent estimated ruminal pH and the ratio of milk protein (%) to milk fat (%) also did not differ between treatments. Although total tract dry matter and nitrogen digestibilities did not differ between treatments, total tract starch digestibility decreased (P < 0.05) when maize was treated with a starch binder compared to the water treatment. It was concluded that the commercial starch binder might not be an effective tool to manipulate total tract maize starch digestion in dairy cows, as is apparently the case with wheat and barley. However, when the prevention of acidosis in dairy cows that receive high amounts of low vitreous maize is the objective, then a starch binder may prove to be effective.
Effect of Pawpaw (Carica papaya) seed meal on the reproductive, endocrine and immune system of Mozambique tilapia (Oreochromis mossambicus)
(Stellenbosch : Stellenbosch University, 2016-03) Omeje, Victor Okonkwo; Lambrechts, Helet; Brink, Danie; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: Aquaculture, the farming of aquatic animals and plants, has the potential to solve the problems of dwindling catches from artisanal fisheries as a result of overfishing and habitat degradation. Tilapia species is one of the most cultured food fish worldwide, second only to carp. In Sub-Saharan Africa, which is in dire need of food security, tilapia has the potential to be a cheap source of protein, which through its cultivation, can contribute to poverty alleviation among the rural poor communities. Tilapia breeds effortlessly in captivity, with this attribute which is considered as the “Achilles heel” of the species, because it predisposes pond systems to overcrowding and low weight at harvest. Efforts to mitigate this shortcoming include mono-sex culture of all-males using exogenous hormone to reverse the sex of sexually undifferentiated fish. This is premised on the fact that improvement in the growth by mono-sex culture will lead to shortened production times and a more uniform weight at harvest, which will ultimately benefit the producers. However, the use of exogenous hormones in aquaculture has recently raised concerns about the effect on farm workers, consumers and on the environment. Recently research has focused on the use of substances of plants origin which mimic the action of hormones as a potential approach to achieve sex reversal in fish. Pawpaw (Carica papaya) seed meal (PSM) contains phytochemicals that hold great promise as a sex reversal and a reproductive inhibition agent in aquaculture. The objective of this study was to determine the optimum inclusion levels of PSM that will produce the highest percentage of male brood when included in the diet of sexually undifferentiated Mozambique tilapia (Oreochromis mossambicus; OM) fry of approximately one to two weeks old. Furthermore the study investigated the effects of the PSM on the reproductive hormone profile, haematological and serum biochemical parameters, and gonad and liver integrity of pre-vitellogenic OM. At an inclusion level of 10 g/kg of basal diet, PSM was able to skew the sex ratio in favour of males (60% males to 40% females). The proportion of males increased with an increasing dosage of PSM, with the maximum masculinization achieved at an inclusion level of 20 g/kg BD, resulting in 77.8% males produced. When the masculinization success was compared in terms of the duration of the feeding regimes of one and four months, no significant differences were observed in terms of the number of males produced. The inclusion of PSM did not affect the growth and survival rates, neither did it affect the Fulton’s condition factor of the treated fish. It was found that the PSM investigated lowered the level of plasma 17β- estradiol in female fish but had no effect on the level of the same hormone in males. The plasma levels of 11-ketotestosterone was not affected in both genders. The gonad weight and gonado-somatic index of the male fish were not affected by treatment with PSM, while the gonad weight, GSI, fecundity and egg diameter of the treated females were lower than those of the control. Some of the changes induced returned to normal on cessation of treatment suggesting a reversible reproductive inhibition by PSM. Haematological and biochemical profiles of different treatment groups did not differ throughout the course of the investigation. Liver weight and hepato-somatic index of the treated fish were comparable to those of the control. Histological observations showed minor alterations in the architecture of the liver, with degeneration and vacuolization of hepatocytes in less than 10% of the members in the group fed 30 g of PSM /kg of basal diet for 60 days. However this was not noticed among the group fed 30 g of PSM/kg of basal diet for 30 days, suggesting a possible reversibility of the lesion on withdrawal of treatment. The current research has clearly demonstrated the potential of PSM as a fertility inhibitor and sex reversal agent in OM, with potential application in rural fish farming and feed manufacturing industries. The possibility exist that some of the findings can be adapted to be applicable in other tilapia species like O. niloticus or Sarotheridon galilaeus which together with O. mossambicus constitute the most cultured species in Sub-Saharan Africa.
Effect of phytogenic feed additives on gonadal development in Mozambique tilapia
(Stellenbosch : Stellenbosch University, 2013-03) Ampofo-Yeboah, Akwasi; Brink, Danie; Lambrechts, Helet; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
ENGLISH ABSTRACT: This study investigated the “Effect of Phytogenic Feed Additives on Gonadal Development in Mozambique tilapia (Oreochromis mossambicus). Aquaculture remains the fastest growing animal food-producing sector and it is set to overtake capture fisheries as a source of food fish, and also to outpace population growth. This rapid growth can be attributed to the increasing demand for aquaculture products, and an urgent need for a sustainable food resource and the safe production of food. Globally, fish provides over 3.5 billion people with up to 15 percent of their average per capita intake of animal protein. The introduction of aquaculture to sub-Saharan African (SSA) took place during the 1940s and 1950s, and the main objectives were to improve nutrition in rural areas, allow for the diversification of activities to reduce the risk of crop failures, to generate additional income, and to create employment opportunities. Aquaculture was seen as a viable option for rural development in SSA, and substantial resources were invested to support its development. Poor results were however, recorded in terms of production and sustainability. Tilapia is the most widely cultured of all fish species farmed, and the second most important group of freshwater and brackish water fish after carps. Tilapia has all the necessary traits that makes it an excellent species to culture, but costefficient production is hampered by the animals attaining sexual maturity at a an early age, which then result in precocious breeding in aquaculture systems. The production of single-sex populations (i.e. all male) is a potential means to address the problem of precocious breeding, but the technologies used to establish single-sex populations are not readily available to resource-poor communities that farm with tilapia for food purposes. Phytochemicals, also known as phytoestrogens, are plant-derived compounds that structurally or functionally mimic mammalian estrogens that affect the sexual differentiation of fish. Phytochemicals occur in plants like Pawpaw (Carica papaya) and Moringa (Moringa oleifera). The study thus had a threefold objective. Firstly, the study investigated the potential of Pawpaw seed meal (P) and Moringa seed meal (M), as part of a commercial tilapia diet, to be used as endocrine disrupting compounds (EDC’s) to control the reproduction of sexually mature Mozambique tilapia (20-45g). Secondly, assess the potential of P and M to inhibit the attainment of sexual maturity in immature tilapia (2-8g). Finally, P and M to determine its influence on sexual differentiation of tilapia fry (9-12 days posthatch) to produce all-male populations. The study indicated that both P and M seeds contain bio-active chemicals that are capable of disrupting the gonad function, differentiation and sexual maturation of Mozambique tilapia. Sperm production was affected, evident in the degeneration of the testicular tissue samples. Egg production, ovulation and spawning were all affected, as evident in the difference in colour of the degrading eggs, as well as the absence of spawning. Ovo-testes were observed in cases where diets containing 10.0g P and 10.0g M /kg basal diet were fed. Eggs were observed in the ovaries of sexually immature fish, but spawning did not occur. The study also presents the first report on the isolation of Oleanolic acid in Moringa seeds. The evident of antifertility properties of both Pawpaw and Moringa seeds can be exploited to control or prevent reproduction of Mozambique tilapia in SSA aquaculture systems. This could be of particular importance to aquaculture development in rural areas of Sub-Saharan African countries, given the abundant year round availability of these compounds. Further studies are required to optimise the preparation of the experimental compounds; as well as determining the optimal inclusion level of the phytogenic compounds, as well as how their efficacy to manipulate the reproductive potential and ability of Mozambique tilapia are influenced by environmental factors such as water temperature.
Effects of cryopreservation of bovine gametes on fertilizing potential and in vitro embryo development
(Stellenbosch : Stellenbosch University, 2007-03) Owiny, David Okello; Barry, Daniel Malan; Coetzer, W. A.; Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Science.
ENGLISH ABSTRACT: Cryopreservation of gametes has significant importance in the advancement of assisted reproductive technologies (ART) in the management of livestock and laboratory animal species, conservation of biodiversity, and treatment of human infertility. Cryopreservation also reduces the cost, genetic drift and diseases associated with maintaining live animals and cell lines. The increasing use of mammalian gametes obtained from the testis, and excurrent ducts, and the ovaries in ART has, therefore, been enhanced by the cryopreservation. There is need to maximize survival of cryopreserved gametes and the ability of cryopreserved gametes to produce embryos. Gametes from bovine ovaries and testes obtained from abattoirs, and culled buffalo testes were used to examine the effects of cryopreservation of gametes on embryo development, and the ability of frozen-thawed African buffalo ( Syncerus caffer caffer) epididymal sperm in in vitro production of cattle x Buffalo hybrid embryos. Effects of a commercial tris-egg yolk-based extender, Biladyl® (BIL) and modified Tyrode's lactate (MTL) on sperm fertilizing potential were compared by evaluating sperm motility, viability, and membrane and acrosome integrity. Tyrode's lactate medium was supplemented with 20 % foetal bovine serum (FBS) and 0.95 M glycerol (GL Y), ethylene glycol (EG) or dimethyl sulfoxide (DMSO). Pre-freezing effects of the extenders and cryoprotectants were minimal in all treatments. Post-thaw parameters were lower (P < 0.05) than the prefreezing parameters and the highest difference (P < 0.0001) was observed after 0 h of equilibration. Post-thaw motility and viability of treatments equilibrated for 2 h and 4 h in MTL, and frozen with GL Y or EG were not different from the control (P > 0.05). Significant differences in post-thaw membrane and acrosomal status occurred between the control and treatments equilibrated for 2 h and 4 h. Using MTL with GL Y or EG, and 2 h or 4 h of equilibration produced results comparable to the control. However, freezing bull epididymal spermatozoa without equilibration is not recommended, and DMSO should only be used in MTL in the absence of GL Y and EG. Bovine epididymal spermatozoa cryopreserved in BIL and MTL after equilibration for 2 h and 4 h was used to inseminate in vitro matured bovine oocytes. In vitro embryo development was assessed to compare the efficacy of BIL and MTL in cryopreserving the fertilizing potential of bovine epididymal spermatozoa. Cleavage rates varied between the treatments, and were lower (P < 0.05) for the treatments than that of the control (BIL). As embryo development progressed, differences between treatments decreased except for sperm cryopreserved in DMSO that maintained a lower (P < 0.0001) development rate than other treatments and the control. Embryo development did not differ (P > 0.05) when sperm equilibrated for 2 h or 4 h was cryopreserved in BIL. However, embryo development was comparable when sperm equilibrated for 2 h or 4 h in MTL was cryopreserved with GL Y or EG. There was no difference in blastomere numbers of embryos of all treatments equilibrated for 4 h. Spermatozoa cryopreserved in MTL containing 0.95 M GL Y or EG, but not DMSO, produced embryos at rates comparable to BIL. Therefore, MTL supplemented with 20% FBS and 0.95 molar concentration of GL Y or EG can be used as a substitute for commercial extender such as BIL for freezing bovine epididymal sperm, and possibly also of other species, for use in ARTs. Frozen-thawed bovine cauda epididymal sperm were subjected to a second freeze-thaw cycle in BIL and MTL, and used for in vitro fertilization (IVF) of in vitro matured bovine oocytes. Cleavage, morula and blastocyst rates were lower (P < 0.05) for oocytes inseminated with sperm that underwent one freeze-thaw cycle in MTL and two freeze-thaw cycles in BIL and MTL (treatments), than the control (one freeze-thaw cycle in BIL). Embryo expansion and/or hatching on days 7-15, were not different (P > 0.05) among the treatments, but embryo expansion and/or hatching on the same days were lower (P < 0.05) when oocytes were inseminated with sperm refrozen in BIL. The blastomere numbers of embryos from sperm of freeze-thaw cycle one in BIL (119 ± 52.8) and MTL (130 ± 43) were not different (P > 0.05) from each other, but were higher (P < 0.05) than that of embryos from sperm refrozen in BIL (58 ± 29). It was concluded that bovine epididymal sperm can be refrozen in BIL, and MTL containing 20 % FBS, EG and used in ARTs. Hybridization between cattle and its closest African wild relative, the African buffalo (Syncerus caffer caffer) was investigated. In an attempt to produce pre-implantation cattle x buffalo hybrid embryos in vitro, matured bovine oocytes were subjected to standard IVF procedure with either homologous bovine (n = 1166 oocytes) or heterologous buffalo (n = 1202 oocytes) frozen-thawed epididymal sperm. After IVF, 67.2% of the oocytes inseminated with homologous sperm cleaved. In contrast, insemination with buffalo sperm resulted in a 4.6% cleavage rate (P < 0.0001). Cleavage was also slower in hybrids than in cattle embryos. Up to 52.2% of the cleaved homologous embryos progressed to the morula stage compared with 12. 7% for the hybrids (P < 0.0001 ). No hybrid embryos developed beyond the 16-cell stage, while 40.1 % of cleaved bovine embryos developed to the blastocyst stage. Developmental anomalies such as polyspermy, uneven cleavage, vacuolization and absence of nuclei in some blastomeres were common in the hybrid embryos. It was concluded that interspecies fertilization of cattle oocytes with African buffalo epididymal sperm occurs in vitro, and that the barrier to hybridization occurs in the early stages of embryonic development. Chromosomal disparity is likely the cause of the fertilization abnormalities, abnormal development and subsequent arrest impairing formation of pre-implantation hybrid embryos. Investigation into the developmental abnormalities including reciprocal hybridization and genetic studies of the hybrid embryos are recommended. The effects of supplementing oocyte maturation medium with 100 μM cysteamine, and the use of a copper-wire cryoloop for vitrification of the in vitro matured bovine oocytes in the production bovine embryos in vitro was examined. Cysteamine did not improved the cleavage rate (P > 0.05), but improved morula and the blastocyst rates (P < 0.05) in one trial. In a second trial, cysteamine did not improve embryo development in the fresh oocytes and the cleavage rate of vitrified oocytes (P > 0.05), but improved the morula and the blastocyst rates (P < 0.05) of vitrified oocytes. Bovine oocytes can be successfully vitrified using a copper-wire cryoloop. Addition of cysteamine in maturation medium improves embryo development of vitrified-thawed mature oocytes. Cysteamine also improves embryo development in non-vitrified oocytes but this effect appears to be influenced by the pre-culture and culture conditions.

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