Characterization of Biological Types of Cattle-Cycle II. IV. Postweaning Growth and Feed Efficiency of Steers2

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Abstract
Postweaning growth and feed efficiency (megacalories metabolizable energy [ME] /kilogram gain) were determined for 798 steers representing Hereford and Angus straightbred (H and A), Hereford-Angus reciprocal cross (HAx), Red Poll-Hereford and Red Poll-Angus reciprocal cross (Rx), Brown Swiss-Hereford and Brown Swiss-Angus reciprocal cross (Bx), Gelbvieh-Hereford and Gelbvieh-Angus cross (Gx), Maine Anjou-Hereford and Maine Anjou-Angus cross (Mx) and Chianina-Hereford and Chianina-Angus cross (Cix) breed groups. Regression of pen mean weight and cumulative megacalories ME on days fed was used to estimate gain, ME consumption and feed efficiency (megacalories ME/kilogram gain) over (1) time- (0 days to 248 days) and (2) weight-constant (250 kg to 470 kg) intervals and to (3) marbling (0 days to a small degree of marbling, USDA choice quality grade) and (4) fat trim (0 days to 18.9% fat trim) endpoints. Breed groups with the most rapid growth rates and heaviest weights at birth, 200 days and 424 days (Bx, Gx, Mx) required fewer (P<.05) megacalories ME/kilogram gain over time- and weight-constant intervals than slower-gaining, lighter breeds (HAx, Rx). Breed groups reaching the marbling or fat trim endpoint in the fewest days generally required fewer .05) megacalories ME/kilogram gain to marbling (HAx < Cix) and fat trim (HAx < Bx, Mx and Cix) endpoints than did faster-growing, heavier breed groups that reached the endpoints at older ages. Contrary to previous reports, HAx did not gain significantly faster than H and A straightbreds during the postweaning period (the HAx advantage was only 2.0% for postweaning average daily gain). HAx required more (P<.05) megacalories ME/kilogram gain than H and A straightbreds over time- and weight-constant intervals. Copyright © 1981. American Society of Animal Science. Copyright 1981 by American Society of Animal Science.

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