Growth and Feed Efficiency of Cattle of Different Mature Sizes

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Abstract
Growth and feed efficiency data were obtained on 146 large and small cattle represented by Holstein and small-framed Angus steers in a serial final weight experiment. Cattle were fed a grain- or silage-based diet in a low maintenance (inside) or a high maintenance (outside) environment. Steers were fed to one of five final weights ranging from 341 to 522 kg for Angus and from 431 to 612 kg for Holsteins. Daily dry matter intake (DDMI) was .67 kg greater (P<.005) for silage-fed than for grain-fed cattle and greater for Holstein than Angus steers. At comparable weights, Holsteins ate .76 kg more (P<.005) dry matter than Angus steers. Weight was a poor predictor of DDMI over these weight ranges, accounting only for 2 to 19% of the variation. Steers fed the grain diet gained .12 kg/day more (P<.001) than silage-fed steers. At comparable weights, Holsteins gained .2 kg/day more (P<.005) than Angus. Dry matter required per unit of gain (DM/G) was 1.79 units greater (P<.005) for silage-fed than for grain-fed steers, and .84 units greater (P<.005) for cattle kept outside than for cattle kept inside. At comparable weights, the small-framed Angus steers required 1 unit more DM/G than Holstein steers. Changes in DDMI, average daily gain (ADG) and DM/G with increasing weight did not differ between cattle of the two mature sizes. ADG declined by .18 kg/day and DM/G increased by 2.2 kg DM/kg gain with each 100-kg increase in body weight. Therefore, different equations for different mature size cattle may not be necessary to predict declines in ADG and feed efficiency associated with increasing weight. Copyright © 1981. American Society of Animal Science . Copyright 1981 by American Society of Animal Science.