Author ORCID Identifier

https://orcid.org/0009-0004-0993-3701

Date Available

11-5-2025

Year of Publication

2025

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College

Agriculture, Food and Environment

Department/School/Program

Animal and Food Sciences

Faculty

Dr. Kristine Urschel

Faculty

Dr. David Harmon

Abstract

Muscle mass is regulated by the balance between muscle protein synthesis and degradation. Previous research in horses has shown that the signaling pathway that regulates protein synthesis is upregulated with increasing protein intake; however, whether this corresponds to an increase in muscle protein synthesis rates had not been previously explored. The objective of this study was to develop an isotopic method to measure muscle protein fractional synthesis rate (FSR) in horses following graded protein intake. Eight mature Thoroughbred horses were studied using a randomized cross-over design. Horses consumed meals containing 0 (No), 0.125 (Low), 0.25 (Med), or 0.5 (High) g protein/kg BW in random order. A 4- hour primed, constant intravenous infusion of [ring-²H₅] phenylalanine measured muscle protein FSR via muscle biopsies taken 1- and 2-hours post-feeding. Plasma glucose, insulin, and amino acids increased over time (P < 0.05). However, there was no dose-dependent response for plasma amino acid concentrations suggesting that even at the lowest amount of protein provided (Low), protein digestion was maximized. There was no effect of treatment on gluteus medius muscle protein FSR (P = 0.96). With further refinement, the stable isotope method is a promising new method for measuring protein synthesis in equine skeletal muscle.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2025.466

Funding Information

This research was funded by the American Quarter Horse Foundation (AQHF) in 2023.

Download

Share

COinS