Production of carcass beef of specified composition in steers of four breeds at three ages

Abstract

The production of carcass beef, where muscle is 80% and dissectible fat 20%, was determined in Hereford, Angus, Friesian and Charolais X steers at 12, 15 and 18 months old fed ad lib, on a commercial pelleted ration from 9 months old to slaughter. The chilled right carcass sides were dissected into muscle, fat and bone. The carcass beef was the weight of dissected muscle plus fat equal to one-fourth that of muscle so that in carcasses with adequate fat the carcass beef was equal to carcass muscle x 5/4. Carcass beef percentage was highest when carcass fat was one-fourth muscle and decreased by 0.92% with each 1% increase in additional fat. There were small breed differences only at constant fatness. Liveweight and carcass weight were poor indicators of carcass beef because a minimum fatness was required and there was a decrease in carcass beef percentage as fatness increased. No one breed was superior at all the ages of slaughter because of the differences in age to reach the degree of fatness necessary to yield carcass beef 80/20. The breeds also differed in rate of fattening and therefore in the rate of decrease of carcass beef percentage with increase in age. The Herefords and Angus were sufficiently fat to be productive at a younger age than the Friesians or Charolais X but were more wasteful with increase in age. The Friesians appeared to grow for a longer time after they were sufficiently fat to be productive of carcass beef, before they became excessively wasteful. It is suggested that where beef production is measured as the yield of carcass beef of a prescribed composition it would reduce production and processing costs.