Abstract:
Sixty Jersey and 48 Friesian bull calves were reared from birth on either of two planes of nutrition. Three calves of each treatment group were slaughtered at liveweights arranged in logarithmic progression between birth weight and 249 kg. The weights of dissectible body parts were regressed on empty body weight after logarithmic transformation of both variates. Treatment effects were tested by comparing the slopes and intercepts of the regression equations. Development of the head, legs, kidneys, and kidney fat differed significantly between these breeds. All of these parts matured earlier in the Jersey. Plane of nutrition affected development of the liver, kidney fat, caul fat, and urogenital tract. These parts were heavier in high plane calves than in low plane calves of the same breed and empty body weight, with the exception of the urogenital tract, where the converse was true. In general, the effects of breed and plane of nutrition on the proportions of carcass and offal components were of minor economic significance.