National estimates of the body composition of British cattle, sheep and pigs with special reference to trends in fatness. A review.
National carcass classification records for cattle, sheep and pigs were used as a basis for estimating the body composition of British livestock slaughter populations. The tissue percentages of carcasses in each classification fatness range were estimated from regression equations constructed using data from breed comparison trials and other sources. The lipid and protein contents of the tissues were then estimated using regression equations from body composition studies. The mean carcass composition, and lean and fat production from current populations (1984) were compared with those of ten years ago. There has been an important increase of 20 kg (8%) in carcass weight for beef but no change in carcass composition. The average beef carcass in 1984 was estimated to contain 23% lipid (inclusive of lipid in perinephric and retroperitoneal fat). The weight of sheep carcasses has fallen by 0·6 kg (3 1 2% ) since 1977 without any appreciable change in carcass composition. The average sheep carcass in 1984 was estimated to contain 24% lipid. The lipid content of the average pig carcass was estimated to have fallen significantly from 27% in 1975 to 22% in 1984, with a small increase in carcass weight.