Body composition of British and Zebu × British cattle in northern Australia 2. Yield of carcass and its relationship to other expressions of composition

Abstract

The variation in yield of carcass of Shorthorn-Hereford (SH), Africander x SH (Ax), Brahman x SH (Bx) and late-castrated Brahman x SH (Bx(late)) steers of the F, generation was examined in relationship to rate of growth and other expressions of composition.On a fasted body-weight basis, yield of carcass was shown to be related to rate of growth. Of the non-dressed-carcass parts of the body, yield of carcass was particularly related to the proportion of gut contents. When this was taken into account, the relationship between yield of carcass and rate of growth was diminished but not eliminated, and breed differences in yield of carcass still remained.Relationships between yield of carcass (relative to the empty body), carcass composition and offal composition are complex, due to the fact that each of these three shape vectors are related to size and rate of growth. Nevertheless, these shape vectors were shown to be related to each other independently of size. However, there was some confounding between the effect of rate of growth on a given shape vector and the effect of the other shape vector, particularly with respect to the relationship between yield of carcass and carcass composition. Nevertheless, it could be said that the proportion of the variation in a particular shape vector that was associated with variation in rate of growth, is explained more simply in terms of variation in another shape.Within breed, animals with a high yield of carcass had a high ratio of muscle to bone plus fascia and tendons in the dressed carcass.The large difference in yield of carcass between breeds.could be accounted for by differences in offal composition, but not by differences in carcass composition. Breed differences in carcass composition at the same size were accounted for by either yield of carcass or offal composition. However, breed differences in the relationship of carcass composition to size were not accounted for by these shape vectors. The effect of yield of carcass on carcass composition was itself accounted for by offal composition.