Protein requirements of growing steers limit-fed corn-based diets.
In Exp. 1, six steers (254 kg) were used in a 6 x 4 incomplete Latin square to determine the effects of solvent-extracted soybean meal alone or in combination with rumen-protected methionine and lysine on N balance in steers limit-fed a high-corn diet to gain 1.1 kg/d. The basal diet contained (DM basis) 80% rolled corn, 15% alfalfa, and .9% urea (13.9% CP), and 2 or 4% soybean meal replaced corn to give CP concentrations of 14.8 and 15.6%, respectively. Each diet was fed with and without 5 g/d of Smartamine-ML (.75 and 2.0 g of rumen-protected methionine and lysine, respectively). Nitrogen retention increased linearly (P = .09) with level of soybean meal. Rumen-protected methionine and lysine had no effect on N balance. In Exp. 2, seven steers (233 kg) were used in a 7 x 4 incomplete Latin square experiment to investigate optimal levels and sources of CP for steers limit-fed to gain 1 kg/d. Treatments included a negative-control diet (urea; 11.7% CP) and six diets containing either 13.5, 15.4, or 17.2% CP with either solvent-extracted or expeller-processed soybean meal. Diets provided 75, 87.5, 100, or 112.5% of estimated CP requirement for a gain of 1 kg/d. The basal diet contained 83% rolled corn, 15% alfalfa, and .2% urea. Nitrogen retention increased linearly (P = .006) with soybean meal addition, and no differences were observed between CP sources. The CP system underpredicted the protein requirements of limit-fed steers under our conditions.
Wessels
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RH
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-1600, USA.
Titgemeyer
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EC
D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D004032:Diet / Q000662:veterinary*; D004044:Dietary Proteins / Q000378:metabolism / Q000592:standards*; D004063:Digestion / Q000502:physiology; D008239:Lysine / Q000032:analysis / Q000378:metabolism / Q000592:standards; D008297:Male; D000455:Medicago sativa / Q000378:metabolism / Q000592:standards; D008715:Methionine / Q000032:analysis / Q000378:metabolism / Q000592:standards; D009584:Nitrogen / Q000378:metabolism; D009751:Nutritional Requirements; D012417:Rumen / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D030262:Soybean Proteins / Q000378:metabolism / Q000592:standards; D014508:Urea / Q000378:metabolism / Q000592:standards; D003313:Zea mays / Q000378:metabolism / Q000592:standards*
D004044:Dietary Proteins; D030262:Soybean Proteins; D014508:Urea; D008715:Methionine; D008239:Lysine; D009584:Nitrogen