Limiting amino acids for growing Holstein steers limit-fed soybean hull-based diets.
Studies were conducted to determine limiting amino acids (AA) for cattle limit-fed soybean hull-based diets. Ruminally cannulated Holstein steers were maintained in metabolism crates, fed the same basal diet (73% soyhulls, 19% alfalfa, DM basis), and given the same intraruminal infusions (400 g/d acetate; to supply energy without increasing microbial protein supply). Treatments were infused abomasally. In Exp. 1, steers (200 kg) were provided 1) water, 2) 10 g/d of methionine (MET), or 3) a mixture of 10 essential AA (10AA). Nitrogen retention (13.7 g/d) was greatest (P < .05) for steers receiving 10AA. Steers receiving MET (7.9 g/d) had greater (P < .05) N retention than control steers (5.4 g/d). In Exp. 2, steers (200 kg) were provided 10AA or 10AA with L-Lys deleted from the mixture. Steers receiving 10AA tended (P < .09) to have greater N retention (19.0 g/d) than those receiving no lysine (16.3 g/d). In Exp. 3, steers (194 kg) were provided 10AA or 10AA with L-Thr deleted from the mixture. Nitrogen retention was not affected by removal of threonine. In Exp. 4, steers (152 kg) were provided 10AA or 10AA with L-His, L-Trp, L-Arg, L-Phe, or branched-chain AA (L-Leu, L-Ile, and L-Val) removed. Nitrogen retention was reduced (P < .05) by removal of either L-His or the branched-chain AA. For steers limit-fed soybean hull-based diets, methionine was first-limiting; histidine, at least one of the branched-chain AA, and possibly lysine were also limiting.
Greenwood
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Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-1600, USA.
Titgemeyer
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EC
D000596:Amino Acids / Q000097:blood / Q000502:physiology*; D000818:Animals; D002417:Cattle / Q000097:blood / Q000254:growth & development*; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000097:blood; D004063:Digestion; D009584:Nitrogen / Q000378:metabolism; D013025:Glycine max; D013912:Threonine / Q000502:physiology
D000596:Amino Acids; D004044:Dietary Proteins; D013912:Threonine; D009584:Nitrogen