Carcass, soft tissue and bone composition of early and late maturing steers fed two diets in two housing types and serially slaughtered over a wide weight range

Abstract

SummarySeventy-one small-framed Angus and seventy-four Holstein steers were chosen to represent small and large mature types in a study designed to provide quantitative information on the effect of breed, diet and housing type on composition of carcasses from cattle slaughtered serially over a wide weight range. Within breed, steers were individually fedad libitumeither a maize-grain or a maize-silage diet and assigned randomly to one of two housing types. The effects of treatments on response variables with increasing carcass weight were tested by covariance analysis.The rate of change of soft tissue chemical composition with increasing carcass weight was not influenced by diet, breed mature size or housing type except for ash which decreased at a faster rate in Angus than in Holstein steers. Percentages of water, protein and ash decreased while lipid increased with increasing carcass weight. At any carcass weight, Angus had more lipid and less water in soft tissue. Percentages of soft tissue protein and ash were affected by diet within breed. The energy content of soft tissue increased with weight and was affected only by breed. Angus soft tissue had more energy than that of Holsteins. Similar results were obtained when the entire carcass was analysed.Cattle fed grain had slightly more water and less ash in bone than cattle fed silage. Angus steers had more protein and ash in bone than Holsteins. Although there was a diet × breed × housing type interaction for lipid content of bone, Holstein bone had higher lipid content than Angus bone for either diet or type of housing. All percentages of chemical components in bone, except water, increased with increasing carcass weight.The experiment showed that large mature-size breeds have the ability to transform a high-energy diet into protein for human consumption. The percentage changes in ash, protein and lipid with increasing carcass weight appeared to follow a pattern of development similar to bone, muscle and fat, respectively, suggesting that Hammond's theory of differential growth holds also for chemical components of bovine carcasses. Bone chemical components, however, had a slightly different developmental pattern. The quantitative information on bone presented herein could be used to exploit bone as a source of human food, dietary supplements and products for bone remodelling surgery.