Heritability of percentage of fast myosin heavy chains in skeletal muscles and relationship with performance.

Summary The purpose of this study was to determine the percentage of fast myosin heavy chains (fast MHCs = MHC 2A+2B) in 2 propelling muscles to estimate the heritability and to identify any relationship with performance. The gluteus medius and the biceps femoris muscles were biopsied in 100 related French Anglo-Arabian horses. The percentages of slow and fast myosin heavy chains were measured using an ELISA technique. The heritability (s.e.) of the fast MHCs percentage was estimated at 13% (0.1) using a restricted maximum likelihood resolution of a mixed animal model. There were significant (P 69.6% fast MHCs) and show jumping (74.1>67.8% fast MHCs) had a higher percentage of fast MHCs in the gluteus medius than poor performers (P<.05). This muscular analysis could be one of the interesting physiological traits to measure for early selection of gallop racing and show jumping horses.