PATTERNS OF CARCASS FAT DEPOSITION IN HEIFERS, STEERS AND BULLS

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Abstract
Seventy-five young, full-fed, Shorthorn-sired cattle (36 heifers, 24 steers, 15 bulls) were slaughtered over a wide liveweight range (150–550 kg) to evaluate the influence of sex on the patterns of fat deposition. Growth coefficients for depot fat relative to half-carcass fat were homogeneous, and there were no differences (P > 0.05) among the adjusted means of depot fat at constant total fat. This indicates that depot fat partitioning among sexes is probably minor, provided comparisons are made at equal fatness. Total rate of fat deposition relative to muscle was similar for heifers and steers, but significantly (P < 0.01) lower for bulls. It is concluded that differences in fattening patterns among sexes result from a combination of fattening at a lighter weight of carcass muscle in heifers than steers and steers than bulls, and from a more rapid rate of fat deposition relative to muscle in heifers and steers than bulls. Relative to half-carcass fat, the rate of fat deposition was greatest in the subcutaneous depot in all sexes followed by intermuscular fat and finally body cavity fat. Relative growth of kidney fat was variable among the sexes, but it was generally similar to the subcutaneous depot. Relative rate of intermuscular fat deposition was greater in the forequarter than the hindquarter, while relative rate of subcutaneous fat deposition was similar in both the fore- and hindquarters.