Dietary crude protein intake influences rates of whole-body protein synthesis in weanling horses

S. L. Tanner, A. L. Wagner, R. N. Digianantonio, P. A. Harris, J. T. Sylvester, K. L. Urschel

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


The objective of this study was to measure whole-body protein kinetics in weanling horses receiving forage and one of two different concentrates: (1) commercial crude protein (CCP) concentrate, which with the forage provided 4.1 g CP/kg bodyweight (BW)/day (189 mg lysine (Lys)/kg BW/day), and (2) recommended crude protein (RCP) concentrate which, with the same forage, provided 3.1 g CP/kg BW/day (194 mg Lys/kg BW/day). Blood samples were taken to determine the response of plasma amino acid concentrations to half the daily concentrate allocation. The next day, a 2 h-primed, constant infusion of [13C]sodium bicarbonate and a 4 h-primed, constant infusion of [1-13C]phenylalanine were used with breath and blood sampling to measure breath 13CO2 and blood [13C]phenylalanine enrichment. Horses on the CCP diet showed an increase from baseline in plasma isoleucine, leucine, lysine, threonine, valine, alanine, arginine, asparagine, glutamine, ornithine, proline, serine, and tyrosine at 120 min post-feeding. Baseline plasma amino acid concentrations were greater with the CCP diet for histidine, isoleucine, leucine, threonine, valine, asparagine, proline, and serine. Phenylalanine, lysine, and methionine were greater in the plasma of horses receiving the RCP treatment at 0 and 120 min. Phenylalanine intake was standardized between groups; however, horses receiving the RCP diet had greater rates of phenylalanine oxidation (P = 0.02) and lower rates of non-oxidative phenylalanine disposal (P = 0.04). Lower whole-body protein synthesis indicates a limiting amino acid in the RCP diet.

Original languageEnglish
Pages (from-to)236-243
Number of pages8
JournalVeterinary Journal
Issue number2
StatePublished - Nov 1 2014

Bibliographical note

Publisher Copyright:
© 2014 Elsevier Ltd.


  • Amino acids
  • Horse
  • Phenylalanine kinetics
  • Protein intake
  • Protein synthesis

ASJC Scopus subject areas

  • Animal Science and Zoology
  • General Veterinary


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