Histochemical and morphometrical characteristics of the Gluteus medius muscle in horses in preparation for jumping competition. Preliminary study

Abstract

Biopsies were taken at depth of 3 and 6 cm in the Gluteus medius muscle of 7 inactive mares and 3 castrated male horses. Age of the animals ranged from 3 to 4 years and none of them had any specific training, 3 months prior to the experiment. The samples were analised with the mATPase miofibrillar technique, to determine the fibrillar composition, and with the NADH-TR technique to determine the oxidative capacity.

The fibrillar composition averages were 16.4%, 36.3%, 29.1% and 18.2% at 3 cm., and 26.9%, 36.1%, 24.7% and 12.3% at 6 cm., for the fibres type I, IIA, IIB oxidative and IIB non oxidative respectively. The fibrillar composition varied in relation to the depth of the biopsy. Type I and type IIB fibres presented significant percentage differences between 3 and 6 cm. Type IIA was similar in percentage at both depths. Horses, in the resting period, presented a higher proportion of type IIB fibres. Oxidative and non oxidative fibres type IIB were not different in percentage at both biopsy depths. The area of the muscle fibres was 2335, 3194 and 5166 um2 for the fibres type I, IIA and IIB respectively. Least diameter was 19, 23 and 28 for fibres type IIA and IIB.

These results indicate that the fibrillar composition of the Gluteus medius muscle in these horses was different to other breeds.