Browsing by Author "Chingala, Gregory"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    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 Crude fat content of baobab seed irrespective of season superseded all the assayed protein sources (P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.