Variability of muscle fibre type composition in a number of genealogical bloodlines in Arabian and Andalusian horses

Abstract

Muscle biopsies were obtained from three different depths of the gluteus medius muscle in 118 horses (33 Arabians and 85 Andalusians), ranging from 42 to 56 months old. All the horses were kept under identical environmental conditions from birth. For each breed, the horses were allotted according to a number of different paternal and maternal bloodlines. Muscle biopsy specimens were analyzed for fibre type distribution (types I, IIA and IIB). Significant differences in muscle fibre type composition were observed among horses belonging to different bloodlines. A very significant influence of the maternal bloodline on the percentages of types I and IIB fibres (P<0.001) was observed in Andalusian horses. In addition, the paternal bloodline had a significant effect on the percentage of type IIA fibres in Arabian and Andalusian (P<0.01 in both) horses. Consistent variations in fibre types were also confirmed between breeds and between sexes. It is concluded that the proportions of equine muscle fibre types are significantly correlated with genetic factors.