CHEMICAL COMPOSITION AND CARCASS SPECIFIC GRAVITY IN CATTLE: EFFECT OF LEVEL OF ENERGY INTAKE AND INFLUENCE OF BREED AND SEX

Abstract

Regression equations to predict the chemical composition of the carcass and empty body from carcass specific gravity were computed for Holstein and Angus cattle fed at two levels of energy (ad libitum or 65–70% of ad libitum). One hundred and forty-one Holstein and Angus bulls, steers and heifers were slaughtered at body weights ranging from 120 to 706 kg and at ages varying from 200 to 650 days. The specific gravity of the right side of the carcass and the chemical composition of the carcass and the empty body were determined. The linearities of the relationships between chemical composition and specific gravity were examined. Sex and breed did not influence (P > 0.05) the relationships between the water, ether extract and energy content of the carcass or empty body and specific gravity whereas the level of energy intake was found to have an effect (P < 0.01). The relationships between the percentage of empty body protein and specific gravity was influenced (P < 0.01) by sex and breed but was not altered (P > 0.05) by the level of energy intake. Relationships between composition and specific gravity were computed using animals containing a minimum of 12% ether extract in the carcass. However, the removal of the leaner animals did not markedly improve (in terms of residual standard error) the precision of prediction of carcass and empty body composition from specific gravity. It was suggested that carcass specific gravity be used to estimate the carcass and empty body composition of groups of animals rather than of individual animals.