Body composition of British and zebu × British cattle in northern Australia 1. Breed and growth rate effects on yield of carcass, dressed carcass composition and offal composition

Abstract

ABSTRACTComparative slaughter was used to assess the body composition of Shorthorn-Hereford (SH), Africander cross (A×), Brahman cross (B×), and late castrated Brahman cross (B×(late)) steers of the F, generation with respect to their yield of carcass, gross carcass composition and offal composition. Animals were slaughtered at pre-determined weights of 315, 355, 399, 449 and 505 kg.The B× animals had the highest carcass yield (expressed either as dressed carcass weight at the same fasted body weight or at the same empty body weight), while the A×, B×(late) and SH animals had similar carcass yield. Within a breed, rate of growth affected carcass yield, with faster growing animals having the lower carcass yield, particularly with respect to fasted body weight.The breeds were different in carcass composition but this was dependent on both size and growth rate. Brahman cross animals had a lower proportion of bone than A× and SH animals, particularly at the higher body weights. Faster growing animals tended to contain more muscle and bone and less fat, with the exception of the SH animals.The breeds were also significantly different in the composition of the offal components. A× were notable for high head weights and low tail weights, B× having high blood weights and low total gut tissue weights, and Bx(late) having high hide weights and low abdominal fat weights.Rate of growth had some effect on offal composition, the general trend being that the faster growing animals were characterized by a lower proportion of heart, blood and pancreas. However there was also evidence that the rate of growth differentially affected the offal composition with respect to breeds. This effect mainly arose because the faster growing B×(late) animals had lower weights of abdominal fat. Within the other breeds, the opposite trend was observed.