Studies on performance and meat quality of indigenous cattle finished on agro processing by products

PhD THESIS

The demand for quality meat is vastly increasing in Tanzania due to expanding market. The attempts to improve meat quality by finishing animals in feedlot using maize grain was unsuccessful due to strong competition with humans for the grains thus alternative feed resources were sought. This study was done with the objective of improving the quantity and quality of meat produced from Tanzania Shorthorn Zebu (TSZ) cattle using agro processing by products. Two experiments were performed to assess the effects of diets containing different agro processing by products on performance and the optimum duration for TSZ cattle to stay in the feedlot. In Experiment One, forty five steers (2.5-3.0 years of age and 200 + 5 kg initial body weight) were randomely allocated to five diets containing agro processing by products. The diets were formulated as molasses based, (molasses with either hominy feed-HFMO or rice polishing -RPMO) or maize meal based (maize meal with either hominy feed -HFMM or rice polishing RPMM), and a control diet of maize meal with molasses -MMMO. The steers were fed the respective diet together with hay and drinking water adlibitum for 90 days after which all were slaughtered and data on carcass characteristics, meat yield and quality were recorded. In Experiment two, fifty steers (3 years of age and 183 + 4 kg initial body weight) were kept in feedlot for 0 (P0), 25 (P25), 50 (P50), 75 (P75) and 100 (P100) days to assess the appropriate period for TSZ cattle to stay in feedlot (n= 10 per period tested). All animals in (P25) to (P100) were fed on HFMO, hay and drinking water on adlibitum basis and data on feed intake and weight gain were recorded. After each feeding period all animals were slaughtered and data on carcass characteristics, meat yield and quality were recorded. Warner Bratzler shear force (WBSF) values were determined on m. longissimus thoracis et lumborum aged for 3, 6, 9 and 12 days at 0◦C. The obtained biological values from both experiments were used to evaluate the economic potential of keeping TSZ cattle in feedlot. The intake of energy (86 + 2.8 (SEM) MJ ME/day) and protein (867 + 29.6 (SEM) g/day) was higher (P < 0.05) for steers on HFMO diet while feed conversion ratio (FCR) was lower (P < 0.05) for steers fed on HFMM (7.87) and HFMO (8.09) diets. The average daily weight gain (814 g), final live weight (274 kg), empty body weight (257 kg) and hot carcass weight (143 kg) were significantly higher (P < 0.05) for steers fed on molasses based diets (HFMO and RPMO) than their counter parts. Though diets had no influence (P > 0.05) on yield of retail cuts, the most tender meat was from steers fed on HFMO diet and meat aged for 9 days. Although the period of stay in feedlot had no effect (P > 0.05) on average daily weight gain and FCR, steers on P100 had greatest daily dry matter intake (7.58 kg). The empty body weight increased by 61% for steers on P100 compared to P0 steers. The heaviest (P < 0.05) hot carcasses (151 kg) and highest dressing percentage (54%) were obtained on P100 steers while the lightest carcasses (91.6 kg) were from P0 steers. Meat from steers under P100 and P75 had lower (P < 0.05) cooking loss and shear force values with faster declined muscle pH than meat from grazing steers (P0). Feed cost per extra unit of meat was higher (6,100 TSh.) for low metabolisable energy intake (MEI) than for high MEI (3,923 TSh.) while the use of high energy diets with high intake for longer periods reduced the cost by 84% compared to the use of low energy diets with low intake. When meat price do not change with feedlot finishing, only high MEI is profitable, and high profit increments are on 50 to 75 days of stay in feedlot. It can be concluded that agro processing by products can successfully replace maize meal in feedlot finishing diets. Feeding of a diet containing hominy feed with molasses to TSZ cattle kept in feedlot for 75 days and carcass ageing of 9 -12 days are the best options for high quantity and quality meat production.