107 Skeletal muscle mitochondrial parameters correlate with sales price in weanling racing-bred Thoroughbred horses

Abstract Thoroughbred horse sales prices rely heavily on animal conformation and ancestral race performance, as well as the current economic landscape. However, little information exists on the relationship between physiological parameters and sales price. We aimed to test the hypothesis that weanling sales price would positively correlate with skeletal muscle mitochondrial parameters in racing-bred Thoroughbreds. Gluteus medius muscle samples were collected from racing-bred Thoroughbred weanlings (n = 19; mean ± SD; 5.7 ± 0.3 mo) and evaluated for mitochondrial volume density (citrate synthase activity; CS) and function (cytochrome c oxidase activity; COX) by colorimetry, and oxidative and electron transport system capacities by high resolution respirometry. Horses were sold at the 2018 and 2019 Keeneland November Breeding Stock Sales at 8.5 ± 0.7 mo of age. Data were analyzed using Pearson Correlation Statistics in SAS (v9.4). Weanling sales price was positively correlated with intrinsic mitochondrial function (COX activity per unit CS; r = 0.6269, P = 0.004) and coupling efficiency with substrates for complex I+II (r = 0.4424, P = 0.05). A trend for a negative correlation was observed between weanling sales price and CS activity (r = -0.4179, P = 0.07), while a trend for a positive correlation between sales price and intrinsic oxidative phosphorylation capacity with complex I substrates (r = 0.3974, P = 0.09) was observed. In this cohort of weanling Thoroughbreds, mitochondrial parameters measured at 6 mo of age correlated with sales price at 8 mo of age. Implications of these relationships as they relate to race performance should be further investigated.