Effect of Level of Energy Intake and Influence of Breed and Sex on Growth of Fat Tissue and Distribution in the Bovine Carcass

Abstract

The rate of deposition of fat and its distribution among the subcutaneous, intermuscular, internal and intramuscular depots were studied in 141 cattle ranging in slaughter weight from 121 to 706 kilograms. Bulls, steers and heifers of the Holstein and Angus breeds were fed at two levels of energy: ad libitum and 65 to 70% of ad libitum. The allometric equations, Y = aXb, was used to examine the effect of energy intake and the influence of breed and sex on the rate of deposition of fat in the subcutaneous, intermuscular, internal and intramuscular depots relative to weight of carcass side or total fat. Group comparisons of fat distribution were made after adjustment by regression to the geometric mean of 18.6 kg of total side fat. Subcutaneous fat was deposited at a faster rate than intermuscular fat. However, among the low energy intake animals, this difference disappeared. Generally, intermuscular fat was the largest depot, followed by subcutaneous, internal and intramuscular fat. Among Holsteins, rates of deposition for subcutaneous, intermuscular and internal fat relative to weight of carcass side were influenced by sex (P<.05). When rate of deposition was expressed relative to total fat, no sex influence was detected (P>.05). In addition, distribution of fat was not influenced by sex. Among Holsteins, the level of energy intake generally did not affect (P>.05) the rate of fat deposition in the individual depots, whereas among Angus, the rates of fat deposition in the subcutaneous and intermuscular depots were generally lower (P<.05) for the animals in the low energy intake group. Among the high energy intake animals, the rates of deposition for subcutaneous, intermuscular and intramuscular fat relative to total fat did not differ (P>.05) between breeds, whereas the rate of deposition for internal fat was faster (P<.05) for Holsteins