EFFECTS OF DIETARY ROUGHAGE LEVEL ON THE FEEDLOT PERFORMANCE AND CARCASS CHARACTERISTICS OF BULLS AND STEERS

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Abstract
An experiment is described comparing bulls and implanted steers fed diets containing three roughage levels (20, 50 and 80% alfalfa–brome hay) with two pens of four cattle in each ’sex’ × dietary roughage level subgroup. Cattle were about 12 mo old and 230 kg at the start of the trial. Each animal was slaughtered when it reached 500 kg. No significant castration × roughage level interactions were found for any of the feedlot or carcass traits studied. Increasing the level of roughage in the diet resulted in a significant decrease in average daily gain (P < 0.01) and an increase in average daily feed (P < 0.01) and feed per kilogram gained (P < 0.01) to 500 kg. Differences in daily digestible energy (DE) consumption and DE and feed cost per kilogram gained were not significant. Increasing the roughage level reduced all measures of carcass fatness (P < 0.05) but had no significant effect on the muscle content. Castration significantly reduced growth rate (P < 0.01) and increased feed requirement per unit of gain (P < 0.05). Steer carcasses were lighter (P < 0.01) and fatter (P < 0.01) than those of bulls and had lighter sample muscle weights (P < 0.01) and smaller sample muscle:bone ratios (P < 0.01).

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