PROTEIN REQUIREMENTS OF BEEF COWS FED PELLETED, GROUND OR CHOPPED BARLEY STRAW IN THE WINTER

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Abstract
Thirty-six pregnant beef cows, mainly crossbreds and from 2 to 10 yr of age, were individually fed straw-based diets containing pelleted, ground and chopped barley straw and three levels of protein in a 3 × 3 factorial experiment. The mean weight gain during the last 84 days of the feeding period in which diets containing 86% straw were fed was 0.28 kg/day/cow. Protein content of the diet significantly affected weight gain (P < 0.05) which increased from 0.18 to 0.37 kg daily when the crude protein content increased from 5.7 to 6.6% (dry matter basis). Cows gained weight more rapidly (P < 0.05) on the pelleted diets although feed intakes were more variable. There were no significant differences in daily feed intakes between diets, the mean being 9.9 kg. Type of diet did not significantly affect calf birth weight or plasma non-esterified fatty acid levels. Low plasma urea nitrogen levels in cows given the low protein diets indicated a protein deficiency.