145 Comparison of skeletal muscle citrate synthase activity across equine breeds

Skeletal muscle citrate synthase (CS) activity serves as a marker for muscle oxidative capacity. CS activity was compared among Quarter Horses (QH), Arabians (AR), Thoroughbreds (TB), Standardbreds and Warmbloods at various ages and stages of training. Gluteus medius muscle biopsies were obtained at ages 6–23 m (n = 10), 2 y (n = 37), 3 y (n = 44) and >3 y (n = 55). Disciplines included reining (QH n = 17), ≥ 50-mile endurance (AR n = 20), racing (TB n = 47, STD n = 14) and dressage (WB n = 15). CS activity was measured fluorometrically. An unpaired t-test or one-way ANOVA compared age groups within breeds and age groups across breeds. A 2-way ANOVA compared breed and age effects across 2 and 3 y-old QH and TB, 3 and 4–7 y-old WB (insufficient numbers of 2 y-old AR and STD). CS was significantly lower in 2 y-old QH than either 2 y-old TB (43% higher, P 3 y in training.