Developmental growth and body weight loss of cattle. II. Dissected components of the commercially dressed and jointed carcass

Abstract

The effects of developmental growth and of body weight loss on the carcass composition of Angus steers, as measured by dissection of butcher's joints, are described. Two groups of steers were used: group A, which grew continuously, and group B, which grew like group A and was then subjected to a period of weight loss before slaughter. Animals in both groups were killed at the same body weights. Statistical analysis consisted of analyses of covariance of weights of components converted to logarithms.

The proportions of muscle and bone decreased significantly as carcass weight increased, while the proportions of all fat components (particularly subcutaneous fat and kidney and channel fat) increased. Developmental growth also influenced the distribution of the components in the carcass, particularly muscle, subcutaneous fat, and intermuscular fat. These changes in weight and distribution of components appeared to be detrimental to carcass value per unit weight. During body weight loss, the weights of bone and of connective tissue remained relatively constant, although with bone the rate of change varied significantly with the size of the animal before weight loss. All other components lost weight, approximately reversing the pattern of development during body weight increase (as estimated from the group A animals). The muscle content of the group B animals was, however, significantly lower than in group A animals at the same carcass weight. Kidney and channel fat also tended to be lower in group B than in group A, but this depended on the size of the animal before undergoing body weight loss. When all fat tissues were considered together, group B carcasses were only slightly lower in fat content than group A carcasses at the same carcass weight, and this difference was not statistically significant. Changes in the distribution of dissected components were also shown to occur with body weight loss. The changes in both weight and distribution of the dissected components appeared to be detrimental to carcass value per unit weight.