Abstract
Lysine has been reported as the first limiting amino acid in typical equine diets. Indicator amino acid oxidation (IAAO) has become the standard method for determining amino acid requirements in other species, but prior to this study, it has not been used to determine equine requirements. The aim of this study was to evaluate whole body protein synthesis and plasma and muscle amino acid concentrations in response to graded levels of lysine intake in yearling horses. Six Thoroughbred colts (358 ± 5 kg) were fed each of six treatment lysine intakes ranging from 76 to 136 mg/kg body weight/day. Blood samples were taken before and 90 min after the morning concentrate meal. Gluteal muscle biopsies were taken ~100 min after the morning concentrate meal. The next day, whole body phenylalanine kinetics were determined using a 2 h primed, constant infusion of [13C] sodium bicarbonate followed by a 6 h primed, constant infusion of [1-13C] phenylalanine. Plasma lysine concentrations increased linearly (P < 0.05) at both the 0 and 90 min time points with increasing lysine intakes. Free muscle asparagine, aspartate, arginine, glutamine, lysine, taurine and tryptophan concentrations responded quadratically to lysine intake (P < 0.05). Phenylalanine kinetics did not differ between treatment intakes (P > 0.10). A broken line analysis of lysine intake and phenylalanine oxidation failed to yield a breakpoint from which to determine a lysine requirement. These diets may have been limiting in an amino acid other than lysine, underscoring the lack of data concerning amino acid requirements and bioavailability data in the horse.
Original language | English |
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Pages (from-to) | 93-100 |
Number of pages | 8 |
Journal | Veterinary Journal |
Volume | 216 |
DOIs | |
State | Published - Oct 1 2016 |
Bibliographical note
Publisher Copyright:© 2016 Elsevier Ltd
Funding
This is publication number 15-07-133 of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. This work is supported by the National Institute of Food and Agriculture , United States Department of Agriculture (grant number 2010-65206-20638 ). Lyn Ennis contributed technical expertise with sample analysis. Preliminary results of this project were presented as abstracts at the Joint Annual Meeting of the American Society of Animal Science and American Dairy Science Association, Phoenix, AZ, USA, 15–19 July 2012, and the Experimental Biology meeting, Boston, MA, USA, 20–24 April 2013. Special thanks to undergraduate interns Elizabeth Deluca and Lindsay Berg for their help with horse care, sampling and laboratory analysis.
Funders | Funder number |
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U.S. Department of Agriculture | 2010-65206-20638 |
US Department of Agriculture National Institute of Food and Agriculture, Agriculture and Food Research Initiative |
Keywords
- Amino acid
- Equine
- Indicator amino acid oxidation
- Lysine
- Protein synthesis
ASJC Scopus subject areas
- Animal Science and Zoology
- General Veterinary