SUNScholar - Browsing by Author "Muller, C. J. C."

Browsing by Author "Muller, C. J. C."

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Effect of energy sources on ovarian follicular dynamics and oestrous activity of Holstein cows
(South African Society for Animal Science, 2018-07-30) Useni, B. A.; Muller, C. J. C.; Cruywagen, C. W.
The objective of the study was to evaluate the effects of three nutritional treatments, which differed in energy level and source, on preovulatory follicles, number of follicles and oestrous activity in dairy cows. Twenty two Holstein multiparous cows from the Elsenburg herd were used in this study. After parturition, cows were kept on kikuyu-ryegrass pastures on an ad libitum basis, and allocated to various levels and types of concentrate supplements, which differed in starch and fat contents. The control group received 7 kg/day of a control concentrate, and the treatment groups each received 12.6 kg/day of concentrate. The concentrates contained high starch-low fat (HSLF) and high starch-low fat/low starch-high fat (HSLF-LSHF) levels. The supplement in treatment HSLF was a glucogenic concentrate using maize as the energy source. The supplements in treatment HSLF-LSHF were a combination of a glucogenic concentrate, which was offered for the first 60 days in milk (DIM), similar to treatment HSLF, followed from 61 DIM by a lipogenic concentrate using wheat bran and calcium (Ca) salts of long-chain fatty acids as the energy sources. At 80 ± 10 DIM, cows were synchronized with an Ovsynch protocol without being inseminated before the ultrasonography observation. While they were detained in a shaded neck clamp, cows were assessed individually with an ultrasound scanner every three days for ovarian measurements and follicular activity until the subsequent oestrus. Results showed that ovarian and follicular measurements and the numbers of follicles in various follicle size classes were similar between nutritional treatments. However, the total ovarian follicular counts were significantly higher in cows that received the HSLF and HSLF-LSHF treatments, compared with their counterparts in the control group (i.e. 7.23 ± 0.22, 7.21 ± 0.14 and 6.53 ± 0.19, respectively), through possible improvement in nutritional status. Further research is required to investigate various energy levels and sources that enhance the viability and the quality of the oocyte ovulating from the dominant follicle and improve the intensity and length of the oestrous expression in dairy cows.
Effect of late prepartum fibre-based diets on the live weight changes and reproduction of Holstein cows in the subsequent lactation period
(South African Society for Animal Science, 2019-03-07) Useni, B. A.; Muller, C. J. C.; Cruywagen, C. W.
The objective of this study was to evaluate two late prepartum fibre-based diets that differed in nonstructural carbohydrate (NFC) and protein levels on live weight (LW) changes and fertility traits of Holstein cows until 120 days postpartum. At 30 days before calving, 120 pregnant Holsteins (heifers, n = 54 and dry cows, n = 66) from the Elsenburg herd were assigned to two nutritional treatments according to parity, expected calving date, LW, and milk production during the previous lactation. Prepartum heifers and cows were fed independently a similar type and level of a prepartum concentrate, associated with an ad libitum intake of either unchopped oat hay for the control group or a partial total mixed ration (pTMR: oat hay (48%), lucerne hay (43%) and soybean oil cake meal (9%)) for the treatment group. After parturition, cows in both the control and treatment groups were maintained on ad libitum cultivated irrigated kikuyu-ryegrass pastures, supplemented each with a post-partum concentrate of 7 kg/day from calving until 120 days in milk (DIM). As expected, young and still growing primiparous cows were significantly lighter in pre- and post-partum LW traits compared with mature multiparous cows (parity > 3). Prepartum LW of cows was similar between the control and the treatment in both parity groups. Post-partum LW of the primiparous cows differed significantly between the control and the treatment, which were 488 ± 9 and 507 ± 13 kg, respectively. However, no difference was observed in terms of post-partum LW of multiparous cows of the control and the treatment groups, which were 579 ± 10 and 579 ± 8 kg, respectively. Primiparous cows that received the prepartum oat hay-based diet showed significant decrease in post-partum LW loss changes, LWnadir, LW loss at nadir and rate of LW loss from calving to LWnadir in comparison with their counterparts on the prepartum pTMR-based diet, but these LW traits were similar in multiparous cows. Prepartum diets did not have an effect on post-partum fertility parameters of the multiparous cows, whereas primiparous cows that received the control diet recorded a significantly longer interval from calving to first service (CFS) in the subsequent lactation in comparison with their counterparts fed the treatment diet i.e. 117 ± 9 and 86 ± 8 days, respectively. Proportions of cows that were pregnant at 120 DIM were similar in the subsequent lactation between groups that received the prepartum oat hay- and pTMR-based diets in both parity groups. Further research is required to investigate different prepartum feeding periods and nutritional approaches involving various levels and sources of energy and protein nutrients to encourage post-partum metabolic and hormonal responses that benefit the fertility of dairy cows in the subsequent lactation.
Effects of energy levels and sources on plasma metabolites and live weight of Holstein cows
(South African Society for Animal Science, 2018-07-30) Useni, B. A.; Muller, C. J. C.; Cruywagen, C. W.
The objective of the study was to evaluate the effects of nutritional treatments, which differed after calving, on energy levels and sources on plasma metabolite profiles and live weight (LW) changes as an indication of the nutritional status in Holstein cows. During the dry period, pregnant heifers (n = 69) and dry cows (n = 153) from Elsenburg Research Farm were maintained under similar feeding and management conditions. After parturition, cows had ad libitum access to cultivated irrigated kikuyu-ryegrass pastures, and were assigned to three concentrate groups, according to calving date, parity, LW and the milk yield of their previous lactation. The groups were supplemented with various levels and types of concentrate, of which the energy was provided by starch and fat. The control group was offered 7 kg/cow/day of a control concentrate supplement for both primiparous and multiparous groups, while concentrates in treatment groups were fed at 11.6 and 12.6 kg/cow/day for primiparous and multiparous groups, respectively. The control supplement was a maize-based concentrate, which contained low levels of starch. The concentrate components of the treatments consisted of high starch-low fat (HSLF) and a high starch-low fat/low starch-high fat (HSLF-LSHF) combination. The HSLF supplement was a glucogenic concentrate, which contained maize as the energy source. The HSLF-LSHF supplements consisted of a glucogenic concentrate, which was offered for the first 60 days in milk (DIM) as per the HSLF treatment, and was followed from 61 DIM with a lipogenic concentrate containing wheat bran and calcium (Ca) salts of long-chain fatty acids as the energy sources. The results showed that all cows mobilized their body fat reserves, as was evident in changes in plasma non-esterified fatty acids (NEFA) before and after calving. Postpartum plasma NEFA and β-hydroxybutyrate (BHB) did not differ significantly between nutritional treatments in multiparous cows. However, the postpartum levels of plasma NEFA and BHB were significantly higher for the control, indicating a status of advanced negative energy balance (NEB) and possible subclinical ketosis compared with HSLF and HSLF-LSHF treatments in primiparous cows. Postpartum plasma urea levels decreased significantly in both primiparous and multiparous animals in the control group, compared with the HSLF and HSLF-LSHF groups. As affected by time, postpartum LW was significantly lowest and LW loss was significantly highest in cows that received the control supplements compared with HSLF and HSLF-LSHF supplements for primiparous and multiparous cows. In addition, LW lossnadir and the number of days to reach it significantly increased in primiparous cows that received the control concentrate, compared with those of the HSLF and HSLF- LSHF treatments. However, this trend was not observed for multiparous cows. The findings of this study showed that HSLF and HSLF-LSHF treatments improved the nutritional status, as was evident in the reduced extent of NEB and limited LW loss of dairy cows, compared with those in the control group.
Fertility in dairy cows and ways to improve it
(South African Society for Animal Science, 2018-11-17) Muller, C. J. C.; Cloete, S. W. P. (Schalk Willem Petrus van der Merwe); Botha, A.
The fertility of dairy cows affects the genetic improvement and financial sustainability of dairy herds. Fertility is a complex trait that is affected by several factors. Genetically, fertility is difficult to improve because of low heritability. Cows that do not become pregnant are usually culled from the herd. This paper reviews results from studies conducted in South Africa that are aimed at improving the reproductive performance of dairy cows. Records from 9 046 cows in 14 Holstein herds showed that, while lactation number, calving year and calving season affected fertility traits significantly, herd management had the largest effect. Mean ± sd for calving to first service (CFS) and from calving to conception (DO) intervals were 77 ± 30 and 134 ± 74 days, respectively. The number of services per conception (SPC) was 2.55 ± 1.79. The proportion of first services within 80 days post partum and cows confirmed pregnant within 100 and 200 days post partum were 0.64 ± 0.48, 0.36 ± 0.48, and 0.71 ± 0.45, respectively. Heritability (h²) estimates were 0.06, 0.08 and 0.07 for CFS, DO, and SPC, respectively. Albeit low h² estimates were consistent with literature results, the genetic correlation between CFS and DO was positive (0.56), and negative (-0.29) between CFS and pregnancy success. Crossbreeding, using a dual-purpose breed, improved fertility, similar to studies conducted overseas. Increasing the energy content of the total diet of Holstein cows on kikuyu-ryegrass pasture by feeding 7 kg versus 12 kg concentrates/cow/day, improved fertility as a higher proportion of cows were pregnant by 150 days in milk, being 0.52 versus 0.84 and 0.56 versus 0.76 for primi- and multiparous cows, respectively. Estimating breeding values for fertility traits for breeding sires would assist in improving fertility in dairy cows
Genetic parameter estimation and breeding plans for the South African dairy goat herd
(Stellenbosch : University of Stellenbosch, 2005-03) Muller, C. J. C.; Schoeman, S. J.; Cloete, Schalk W. P.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Animal Sciences.
Milk production records of all grade and registered Saanen dairy goats from the Milk Recording and Performance Testing Scheme of the Animal Improvement Institute of the Agricultural Research Council of South Africa and pedigree information of these animals from SA Studbook were analyzed to obtain specific genetic parameters. Records of goats with lactations exceeding 60 days in milk were used. A sufficient number of records only became available from 1985 onwards. Reproduction records were determined from milk recording data. The number of milk production records for the British Alpine and Toggenburg breeds was too small to warrant a genetic evaluation. In total, 3190 lactation records of 1413 Saanen does were available for the initial analysis. First and second parity records, 1190 and 775 records, respectively, were subjected to a separate genetic analysis. Milk production records (2319) of one commercial herd providing more than 70% of all the records in the national herd, were also subjected to a separate genetic analysis. The fixed effects identified as having a significant (P<0.05) effect on all traits studied were production year, age of dam, lactation length, parity number, herds (owners) and year of birth. Although some significant interactions were found, they were ignored as their effects were very small. Additive genetic variances and heritability estimates were obtained by ASREML procedures fitting three models. Estimates were generally in accordance with values found in the literature although estimates for fat and protein percentage were lower than expected when compared to dairy cow data. This could be explained by pedigree information lacking in the data set. The h2 estimate for milk yield using all records, first parity records, second parity records and records from a commercial herd were 0.21±0.05, 0.32±0.08, 0.20±0.10 and 0.31±0.06, respectively. Heritability estimates for fat percentage showed a large variation and were 0.19±0.05, 0.67±0.08, 0.34±0.12 and 0.12±0.05, respectively for similar data sets as previously mentioned. In contrast to this protein percentage varied little between data sets and were 0.30±0.06, 0.32±0.00, 0.24±0.11 and 0.28±0.07, respectively. Genetic and phenotypic correlations among production traits were positive and high for all data sets. As for dairy cows, milk fat and protein percentages were negatively related to milk yield. Genetic correlations between milk fat and protein percentages were positive and moderate to high. Increasing milk volume would have a negative effect on fat and protein percentages although it would increase fat and protein yields. Reproduction parameters, i.e. age at first kidding (AFK), age at last kidding (ALK), productive life (PL) and number of lactations (NL) were derived from milk recording data. Mean values for these parameters were 457±171 days, 1046±718 days, 19.3±13.9 months and 2.24±1.37 kiddings, respectively. Kidding interval had no genetic basis and is controlled by management. Heritability estimates were in accordance with literature values and were 0.25±0.04, 0.28±0.04, 0.08±0.04 and 0.05±0.03 for AFK, ALK, PL and NL, respectively. The genetic correlation between AFK and ALK was as expected positive and high, i.e. 0.61±0.10, although the correlation between AFK and PL was negative indicating similar to dairy cows that PL is shortened by a later AFK. The genetic trend for milk, fat and protein yield were positive, although it did not differ from zero. Large variations were observed between years (R2 <0.13). Genetic trends for fat and protein percentages were positive and negative (P<0.05), respectively. These trends are in contrast to trends observed in other countries such as France, The Netherlands and the USA where positive trends were generally observed. This may indicate a higher selection emphasis on milk yield parameters or more complete data sets in terms of pedigree information. The dairy goat industry in South Africa should address some of the problems that were encountered in the analysis of the data. These include factors such as a large number of small herds, many short lactations, a large number of animals lacking production data linked to pedigree information, incomplete pedigrees, few does that have completed three or more lactations, little genetic ties between herds and a small number of progeny for bucks. Some organizational and logistic issues concerning pedigree and milk recording need to be addressed by the South African Milch Goat Society to enable the accurate estimation of the genetic merit of animals in the national herd.
Milk production of dairy cows as affected by the length of the preceding dry period
(South African Society for Animal Science, 2014-08-22) Useni, B. A.; Muller, C. J. C.; Cruywagen, C. W.
The objective of the study was to determine the effect of the duration of the dry period (DP) on the milk yield and milk composition during the following lactation. Milk performance records of 561 Holstein cows, with a previous DP from the Elsenburg Research Farm obtained from the National Milk Recording Scheme, were used in the study. Four groups of dairy cows were identified, based on the duration of their dry period, i.e. cows with a DP of less than 60 days, DP of 61 to 90 days, DP of 91 to 120 days and DP of more than 121 days. The number of records for each group was 76, 162, 83 and 240 lactations, respectively. An ANOVA was conducted using the Generalized Linear Model of SAS to compare milk yield and milk composition according to the DP length. Almost 43% of cows had a DP longer than 121 days, while less than 14% of cows had a DP of less than 60 days. The milk yield was positively affected by DP length. Cows with a DP of less than 60 days produced less milk than cows with longer (more than 61 days) dry periods, e.g. 6462 ± 321 vs. 7393 ± 99 kg. Results were similar for cows in their second and fourth parity. In addition, the milk composition of cows was also affected by DP length, i.e. higher fat and protein levels in the milk from cows with a short DP. Cows in the third lactation with a DP above 121 days produced more milk than the other DP groups. However, the milk composition of cows in the third lactation was not affected by DP length. A DP of less than 60 days reduced milk yield, while an extended DP of more than 121 days would be costly for the dairy farmer even though milk yield was higher. A long dry period may also result due to an excess body condition and calving complications during the subsequent lactation.
Non-genetic factors affecting fertility traits in South African Holstein cows
(South African Society for Animal Science, 2014-03-08) Muller, C. J. C.; Potgieter, J. P.; Cloete, S. W. P. (Schalk Willem Petrus van der Merwe); Dzama, K.
Profitable milk production and genetic improvement in dairy herds depend largely on fertile cows calving annually to initiate a new lactation period. Over the last 30 years, several studies have indicated a decline in the reproductive performance of dairy cows. From the perspectives of many farmers and veterinarians, the reproductive performance of cows is related to the calving interval (CI) and services per conception (SPC). Using these traits as cow fertility indicators is problematic as CI is dependent on subsequent calving dates, while SPC is strongly linked to inseminator proficiency. Cow fertility refers to the ability of cows to come into oestrus soon after calving, to conceive from a minimum number of services, and to stay pregnant until the next calving. In this paper, non-genetic factors affecting fertility traits other than CI in Holstein cows are discussed. Service records (n = 69 181) and pregnancy check results of 9 046 cows in 14 herds were available. Six fertility traits were derived. Means (± sd) for the interval traits, namely calving to first insemination (CFS) and the interval from calving to conception (days open (DO)) were 77 ± 30 and 134 ± 74 days, respectively, while the number of SPC was 2.55 ± 1.79. The proportion of first services occurring within 80 days post partum (FS80d) and the proportion of cows being confirmed pregnant within 100 days (PD100d) and 200 days post partum (PD200d) were 0.64 ± 0.48, 0.36 ± 0.48 and 0.71 ± 0.45, respectively. While lactation number, calving year and calving season affected reproduction traits significantly, herds (management) had the largest effect.
Pre- and postpartum effects of starch and fat in dairy cows : a review
(South African Society for Animal Science, 2018-01-30) Useni, B. A.; Muller, C. J. C.; Cruywagen, C. W.
This review discusses the effects of starch and fat before and after calving on metabolism, energy balance (EB), milk production, and reproduction in dairy cows. The shift in dairy cows from a pregnant non-lactating state to a non-pregnant lactating state induces physiological changes, which affect the metabolic and endocrinal axes to redirect body energy stores towards the mammary gland for milk production. Overfeeding high starch and fat levels during the dry period after calving may result in cows failing to adapt to the negative energy balance (NEB) because of major liver and rumen dysfunction. Alternatively, keeping dry cows on high-forage/low-energy diets adjusts dry matter intake (DMI) to optimize the rumen function and decrease the severity of the NEB during transition. These periparturient biological improvements in dairy cows showed real benefits such as fewer postpartum health complications (e.g. milk fever, ketosis, mastitis, metritis), decreased body condition loss and improved reproductive axis in the subsequent lactation. Adding dietary starch and/or fat to diets of dairy cows following parturition increased milk yield. In addition, milk protein of dairy cows increased with glucogenic diets, but decreased with lipogenic diets. Inversely, milk fat usually increases after feeding lipogenic diets, but it decreases when feeding glucogenic diets to dairy cows. Glucogenic and lipogenic nutrients can affect the cow’s metabolism and its EB status positively, as is evidenced by plasma non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), glucose, amino acids, insulin, insulin-like growth factor-I (IGF-I), growth hormone (GH), gonadotropin hormones, and progesterone (P4) levels. These metabolites (NEFA, BHB, glucose, amino acids) and hormones (insulin, IGF-I, GH, P4) have been shown to affect folliculogenesis, ovulation, conception, and pregnancy success. Feeding a starch-based diet to dairy cows can lead to acidosis and increase glucose and insulin levels, while decreasing NEFA and BHB levels. Furthermore, an insulinogenic diet favours an early resumption of ovarian activity, but has adverse effects on the quality of oocytes. In contrast, keeping dairy cows on a fat-based diet elevates NEFA and BHB levels and decreases glucose and insulin levels. Additionally, a lipogenic diet increases the plasma P4 levels and improves the quality of oocytes. These evidences suggest that reproductive performances in dairy cows can be enhanced by feeding an insulinogenic diet until the resumption of the ovarian cycle then switching to a lipogenic diet from mating period onwards. Since long-term field studies on fertility are limited and the reproduction process in dairy cows is multi-factorial, further research is needed on the pre- and postpartum effects of starch and/or fat as well as their combinations on reproduction axis and thus to draw conclusions on reproductive performances.
Random regression test-day model for the analysis of dairy cattle production data in South Africa : Creating the framework
(South African Society for Animal Science, 2010) Dzomba, E. F.; Nephawe, K. A.; Maiwashe, A. N.; Cloete, S. W. P. (Schalk Willem Petrus van der Merwe); Chimonyo, M.; Banga, C. B.; Muller, C. J. C.; Dzama, K.
Genetic evaluation of dairy cattle using test-day models is now common internationally. In South Africa a fixed regression test-day model is used to generate breeding values for dairy animals on a routine basis. The model is, however, often criticized for erroneously assuming a standard lactation curve for cows in similar contemporary groups and homogeneity of additive genetic variances across lactation and for its inability to account for persistency of lactation. The random regression test-day model has been suggested as a more appropriate method and is currently implemented by several Interbull member-countries. This review traces the development of random regression methods and their adoption in test-day models. Comparisons are drawn with the fixed regression test-day model. The paper discusses reasons for suggesting the adoption of the random regression approach for dairy cattle evaluation in South Africa and identifies the key areas where research efforts should focus. .
Ruminal protein and fibre degradability of lucerne hay as affected by regrowth period and dairy breed
(South African Society for Animal Science, 2011) Cruywagen, C. W.; Muller, C. J. C.; Du Toit, F. J.
The chemical composition of roughages constantly changes while it grows towards maturity. The effective dry matter (DM), crude protein (CP) and neutral detergent fibre (NDF) degradabilities of lucerne hay (LH), harvested after regrowth periods of 4, 5 or 6 weeks, were determined in ruminally cannulated Holstein and Jersey cows by using the in sacco nylon bag technique. The degradabilities of DM and NDF across breeds differed between the LH harvested after the regrowth periods of 4, 5 and 6 weeks. Increasing the regrowth period of LH from 4 to 6 weeks significantly reduced effective DM degradability (k p = 0.08) from 59.0% to 51.2% and NDF degradability from 30.8% to 21.2%. Crude protein degradability tended to decrease with advancing maturity, with values of 77%, 73% and 74% after 4, 5 and 6 weeks' regrowth, respectively. Effective degradability of DM, CP and NDF did not differ between Holstein and Jersey cows. The results from this study suggest that LH harvested after a shorter regrowth period is of a higher quality in terms of DM, CP and NDF degradability which decreases as the plants mature.

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