A COMPARISON OF THE GROWTH AND CARCASS CHARACTERISTICS OF STEERS REARED ON PASTURE AND FINISHED FOR VARYING PERIODS ON CORN OR GRASS SILAGE

Abstract

Sixty small-framed yearling Hereford and Hereford cross steers initially averaging 268 kg were reared on pasture from May to October, divided into two (30 each) approximately equal weight groups and placed in a feedlot. The steers were serially slaughtered in groups of 10 (five heaviest from each treatment) after 0, 35, 70, 98, 126 or 154 days of feedlot finishing on either grass or corn silage supplemented with 0.9–2.3 kg-head−1∙day−1 of a mixed grain ration containing 5% molasses. Average gains on pasture were 0.80, 0.75 and 0.54 kg/day for the consecutive 59, 48 and 61 day periods between 9 May and 24 Oct. Steers finished on corn silage gained significantly faster (P < 0.05) and had significantly more dissectable rib fat when slaughtered (0.82 kg/day; 27.6%) than steers finished on grass silage (0.51 kg/day; 24.6%). Six of the 10 steers slaughtered off pasture graded B1 or C1 while one of the feedlot steers graded B1 and the remaining 53 graded A1 or A2. The subjective carcass fat color score of the steers slaughtered off pasture averaged 4.7 which was significantly greater than the fat color of the feedlot finished steers (3.0–3.6). The corn silage steers had a color rating of 3.4 while the grass silage steers rated 3.7. The results of this experiment indicate that yearling steers reared on pasture and finished between 35 and 70 days on grass or corn silage with low concentrate supplementation will produce acceptable carcasses in terms of grade and subjective fat color score. Key words: Growth, carcass characteristics, steers, pasture, silage