Effect of genotype and feeding system on carcass characteristics an meat quality of Ankole cattle, Mubende goats and their crossbreeds
The main objectives of this study were to; establish effects of genotype and feeding system on carcass characteristics and meat quality and to investigate effects of postmortem storage on textural tenderness of meat from Ankole cattle, Mubende goats and their crossbreds. Experiment I evaluated effects of genotype and feeding system on carcass characteristics and meat quality of Ankole cattle and their crossbreds with Boran and Friesians. A 3x3 factorial treatment arrangement was used to randomly allocate 144 aged 18 months bulls; 48 pure Ankole (A), 48 AnkolexBoran (AXB) and 48 AnkolexFriesian (AXF) crossbreds, to three feeding systems sole grazing (GZ), grazing with supplementation (GZS) and feedlot (FL) with bulls fed ad libitum on maize stover and supplement. Carcass measurements including carcass weights, carcass length, internal chest width, hind-limb length and maximum hind limb width were measured. Palatability attributes were assessed by consumer and trained panels and textural tenderness was measured by the Warner-Bratzler shear force machine. Carcass weights, hind quarters, blockiness indices were higher in AnkolexBoran bulls than in Ankole and AnkolexFriesian bulls. Ankole and Friesian crossbred bulls had higher muscle percentages than Boran crossbreds. Shear force values were highest in Boran crossbreds between 2 to 7 days of ageing and past 14 days shear force values were no longer different (P> 0.05) among genotypes. Steaks from Ankole and Friesian crossed were more tender, juicer and palatable than steaks from Boran crossbreds. With regard to feeding system, carcass weights, hind quarters, blockiness indices and fat percentages were higher in supplemented grazing and feedlot bulls than in sole grazed bulls but muscle percentages were higher in sole grazed bulls. Steaks from grazed bulls were less tender, juicer, palatable and acceptable than steaks from grazed and supplemented bulls. Steaks from feedlot and supplemented Ankole and Friesian crossbreds required 7days of ageing to become tender whereas steaks from Boran crossbreds required 14 days of ageing to become tender. However, when finished in a feedlot, steaks from Boran crossbreds became tender in 7days of postmortem storage. Based on the results of this study, it was concluded that supplementation of grazing cattle and feedlot finishing of previously rangeland grazed cattle improved carcass quality of indigenous cattle in Uganda. Ageing of beef up to 7 days would also improve meat tenderness of beef from indigenous cattle breeds in Uganda. Experiment II evaluated genotype and feeding system effects on carcass characteristics, composition and meat tenderness of Mubende goats and their Boer crossbreds. A 2x3 factorial arrangement was used to randomly allocate 60 castrates between 9-12 months of age, 30 purebred Mubende (M) and 30 MubendeXBoer (MXB) to three feeding systems; sole grazing (GZ), grazing + concentrate1 (GZC) and grazing + molasses based concentrate (GZM). Crossbreds had heavier longer carcasses with bigger hind quarters and blockiness indices than Mubende goats. However, Mubende and Boer crossbreds did not differ with regard to carcass component percentages and meat tenderness at all ageing times. The results also showed that supplementation of grazing goats increased carcass weights, improved carcass grades, hind quarters muscular and blockiness indices. Steaks from both genotypes were equally accepted by consumers. Shear force results also showed that steaks from both genotypes were objectionably tender. Grazed goats produced tough meat which was rated as less juicy and palatable by consumers than meat from supplemented goats. A similar trend was observed with shear force results, meat from supplemented goats had lower shear force values than grazed goats. From the study, it was concluded that supplementation of rangeland grazed goats improved carcass and meat quality. Based on the results from both experiments, it was concluded that Ankole cattle and Mubende goats have an inherent potential to produce good quality carcasses and meat when finished in a feedlot and supplemented as their crossbreds. Postmortem storage of 7 days is recommended for meat from supplemented Ankole bulls and feedlot finished AnkolexBoran crossbreds. Incases where animals are slaughtered directly from rangelands without any feedlot finishing, meat from Ankole, AnkolexBoran and AnkolexFriesian crossbreds should be stored for 14, 21 and 7days respectively. Where goats are also slaughtered directly from rangelands without any supplementation prior to slaughter, meat should be aged for 7 and 14 days for Mubende and MubendeXBoer crossbreds respectively.