FEEDLOT PERFORMANCE AND CARCASS COMPOSITION OF CULL COWS OF DIFFERENT AGES

Abstract

Two experiments were conducted to study the effect of age on the feedlot performance and carcass characteristics of cull range cows. In the first experiment, 87 cull cows of three breed-types (Hereford, Beef Composite and Dairy Composite) and three age groups (young, intermediate and mature) were fed a grain diet for 0, 8 or 16 wk. Rate of gain was higher (P < 0.01) in the first than in the second 8 wk (1.80 vs. 1.13 kg−1∙head−1∙day−1). This was accompanied by an increase (P < 0.01) in feed:gain ratio (6.9 vs. 12.8). There were no significant differences among breeds or age groups in feedlot performance or carcass characteristics. Carcass weight increased with age (P < 0.01) and length (P < 0.01). When adjusted to a common carcass length, mature cows had smaller rib eye areas than the other cows. In the second experiment, 37 cull range cows of predominantly Angus breeding, and representing two age groups (young and mature) were used. Twenty-nine of these cows were fed a grain diet ad libitum for 8 wk before slaughter. Young cows gained 1.61 kg∙head−1∙day−1 compared with 1.29 kg∙head−1∙day−1 for the mature cows. The initial level of body fat had no apparent effect on subsequent feedlot performance. The 9th- 10th- 11th rib joints of the younger cows contained less bone (P < 0.01), and had higher muscle:bone ratios (P < 0.01) than those from the mature cows. Key words: Cull cows, feedlot performance, compensatory growth, carcass composition