| dc.description.abstract | Research regarding factors that impact musculoskeletal characteristics of horses is sparse. Therefore, we conducted four experiments to assess potential effects of breed, exercise training, complexed trace mineral supplementation, transportation stress, age and thyroid stimulating hormone concentration on a) mitochondrial density and function, b) oxidative stress and antioxidant status and c) muscle fiber type and size in various age groups of horses. Relative to weanling Standardbred and Thoroughbred horses, weanling Quarter Horses had lower integrated maximum oxidative and electron transport system capacity (P ≤ 0.02), and the three breeds differed with regard to contribution of mitochondrial complexes to oxidative capacity. In a study of yearling Quarter Horses, transportation stress elevated serum creatine kinase activity (P < 0.0001; a marker of muscle damage), and muscle malondialdehyde concentration (P ≤ 0.009; a marker of oxidative stress). However, complexed trace mineral supplementation increased muscle antioxidant activity, as measured by glutathione peroxidase activity (P ≤ 0.02), in yearling Quarter Horses.
Compared to young horses, aged horses exhibited higher citrate synthase (CS) activity (P = 0.04), but lower cytochrome c oxidase (CCO) activity (P = 0.04), and a lower percentage of type IIx muscle fibers (P = 0.03). Exercise training increased CS activity (P ≤ 0.003), CCO activity (P = 0.04), and maximum oxidative capacity (P ≤ 0.006) in young and aged horses, and increased the percentage of type IIx fibers in aged horses (P < 0.0001). In an ex vivo study of equine skeletal muscle in mature and aged horses, 10 mIU/mL of TSH increased maximum oxidative capacity (P ≤ 0.007). Together, these data provide a wealth of information regarding factors that impact musculoskeletal l characteristics in throughout the lifetime of horses. | |
