Free amino acid supplementation to steers: effects on ruminal fermentation and performance

J Anim Sci. 1997 Apr;75(4):1167-78. doi: 10.2527/1997.7541167x.

Abstract

Three studies were conducted to evaluate amino acid utilization by cattle. In Exp. 1, five steers (580 kg) were fed 86% rolled corn diets with mixtures of amino acids containing up to 6 g/d DL-Met, 24 g/d L-Lys, 6 g/d L-Thr, and 3 g/d L-Trp. Treatments had little effect on ruminal fermentation, diet digestibility, N flow to the duodenum, or microbial efficiency. Ruminal concentrations of Met and Lys increased linearly (P < .05) with amino acid supplementation, whereas Thr responded quadratically, and Trp was not altered. In Exp. 2, four steers (414 kg) were used to measure effects of dietary monensin or laidlomycin propionate in high-grain diets supplemented with amino acids. Ionophores had no significant effect on ruminal fermentation or outflows of amino acids from the rumen. In Exp. 3, 100 steers (287 kg initial BW) were fed diets containing 1% of a nonprotein N source. Treatments were 1) no supplemental N (UREA), 2) UREA plus soybean meal (SBM), 3) UREA plus 2 g/d DL-Met, 8 g/d L-Lys, 2 g/d L-Thr, and 1 g/d L-Trp, or 4) UREA plus 4 g/d DL-Met, 16 g/d L-Lys, 4 g/d L-Thr, and 2 g/d L-Trp. During the growing period (diets based on whole-plant milo silage), gains were higher for SBM-supplemented steers than for UREA steers and intermediate for steers supplemented with amino acids. Few significant differences in performance were observed among treatments during the finishing phase (diets based on dry-rolled corn) or for the entire experiment, but cattle fed SBM or amino acids tended to be fatter and have better marbling scores and quality grades. Amino acids did not greatly alter ruminal fermentation or cattle performance.

MeSH terms

  • Amino Acids / administration & dosage
  • Amino Acids / metabolism
  • Amino Acids / pharmacology*
  • Animal Nutritional Physiological Phenomena
  • Animals
  • Body Composition / drug effects
  • Body Composition / physiology
  • Cattle / growth & development*
  • Cattle / metabolism*
  • Cattle / physiology
  • Diet / standards
  • Diet / veterinary
  • Digestion / drug effects
  • Digestion / physiology
  • Edible Grain / standards
  • Fermentation / drug effects
  • Fermentation / physiology
  • Food, Fortified
  • Ionophores / pharmacology
  • Lysine / administration & dosage
  • Lysine / metabolism
  • Lysine / pharmacology
  • Male
  • Methionine / administration & dosage
  • Methionine / metabolism
  • Methionine / pharmacology
  • Nitrogen / metabolism
  • Rumen / drug effects
  • Rumen / metabolism
  • Rumen / physiology*
  • Threonine / administration & dosage
  • Threonine / metabolism
  • Threonine / pharmacology
  • Tryptophan / administration & dosage
  • Tryptophan / metabolism
  • Tryptophan / pharmacology
  • Urea / administration & dosage
  • Urea / metabolism
  • Urea / pharmacology

Substances

  • Amino Acids
  • Ionophores
  • Threonine
  • Tryptophan
  • Urea
  • Methionine
  • Lysine
  • Nitrogen