Realimentation of Cull Range Cows. 2. Changes in Carcass Traits

Abstract

Carcasses from cull range cows used in three separate trials were evaluated. The cows, 4 to 10 years of age were all thin at the initiation of the feeding period. In two of the three trials, animals were slaughtered prior to the feeding period to obtain base values for carcass traits. In trial 1, the cows were fed an 80% concentrate diet for 38 to 108 days in order to obtain a wide range in final slaughter condition. In trials 2 and 3, the cows were fed to an approximate constant condition on diets varying in concentrate level. The left sides of all carcasses were separated into wholesale cuts which were weighed and the boneless portion analyzed for fat and protein. Initial carcass weights of cows between trial 1 and 3 varied from an average of 208 to 123 kg, respectively. Carcasses from fed cows in the same groups ranged from 290 to 200 kilograms. The portion of individual wholesale cuts, except for the round and shortloin, were similar (P>.05) for fed and nonfed groups. Total increases in fat thickness produced during the trials were minimal and only for cows fed for 108 days in trial 1 did it exceed 1 centimeter. Marbling scores were higher (P<.05) for fed cows and the increased amounts observed were more closely associated with time on feed rather than level of concentrate in the diet. Ribeye area tended to increase for realimented cows. Weight gains were found throughout the entire carcass, with plate, rib, loin and flank demonstrating the greatest weight increase. Percentage protein for most wholesale cuts decreased (P<.05) with increasing weight. For all wholesale cuts and groups of fed cows, percentage lipid increased (P<.05). Carcass composition determined by physical separation of lean, fat and bone was accurate when fat deposition was low, but deviated from chemical lipid and protein determinations as carcass fat content increased to 35% when expressed on a boneless basis.