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Effects of Ration Protein Level and Diethylstilbestrol Implants on Early-Weaned Beef Bulls¹

Iowa State University³, Ames 50010

Abstract

The effects of early weaning (3.5 vs 7 months), diethylstilbestrol (DES) implantation and ration protein level on beef bull calves were evaluated. Protein levels compared in a 90% concentrate ration were: 14% vs 12%, initial weight to 400 lb (182 kg); 13% vs 11%, 400 lb (182 kg) to 800 lb (364 kg); 12% vs 10%, 800 lb (364 kg) to slaughter. In both trials, half of each weaning group received 45 mg DES at 205 and again at 317 days of age; in trial 2, half of each weaning group was implanted with 45 mg DES at 3.5 months. All were slaughtered at 52 to 53 weeks of age. Early-weaned calves gained faster (P<.01) from 106 to 205 days of age than calves left with their dams to 205 days: 2.72 lb (1.24 kg) vs 2.09 lb (.95 kg)/day, respectively. Feed efficiency for early-weaned calves was 4.5. There was no apparent response to high protein or DES implants during the early-weaned period. Standard-weaned calves gained faster (P<.05) from 206 days of age to slaughter: 2.77 lb (1.26 kg)/day vs 2.53 lb (1.15 kg)/day, and more efficiency: 6.3 vs 6.8 than early-weaned calves. During this period, feeding high protein rations slightly improved the daily gain of early-weaned calves, but not the standard-weaned calves. From 3.5 months to slaughter, there was no weight gain response to the high-protein rations. DES implants had no effect on gain, carcass grade or number of carcasses discounted as stags. No stag carcasses were found from 38 early-weaned calves vs seven stags from 40 standard-weaned calves. Implanted bulls were fatter (P<.05) over the longissimus, but differences in total carcass ether extract were not statistically significant. Rib steaks from standard-weaned calves were rated more tender (P<.01) than from early-weaned calves; flavor, juiciness and overall evaluation were similar between treatment groups.

¹ Journal Paper No. J-7301 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 1762.

² Present address: Farmers Friend Mineral Co., 1048 East Main Street, Louisville, Kentucky 40206.

³ Department of Animal Science.

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