THE FEEDLOT PERFORMANCE AND CARCASS COMPOSITION OF YOUNG AND MATURE CULL HOLSTEIN COWS

Abstract

Twelve young and twelve mature lean Holstein cows were fed a high energy diet to appetite based on high moisture corn and haylage. In addition to the cows put on feed, six young and six mature cows were slaughtered at the start of the trial to estimate initial body composition. After 68 days on feed, two young cows and two mature cows were slaughtered on a weekly basis until the conclusion of the trial. Mature cows were initially 45 kg (P < 0.5) heavier than young cows and this difference had increased to 57 kg at the conclusion of the trial. There were no significant differences between young and mature cows in average daily gain (1.37 vs. 1.48 kg/day) or dry matter feed conversion rate (8.46 vs. 8.31 kg DM/kg gain). Average daily dry matter intake was higher (P < 0.05) for mature cows than young cows. There was no decline in average daily gain during the feeding period, although dry matter feed conversion increased for both young and mature cows. There were few differences between young and mature cows slaughtered initially and those slaughtered after the feeding period in carcass composition, and the carcass characteristics that were measured. Young cows, however, had significantly (P < 0.5) higher carcass grades after a feeding period. The feeding period resulted in a decreased proportion of lean and bone and an increased proportion of fat in all the major fat depots (subcutaneous, intermuscular, body cavity fat).