HISTOCHEMICAL AND MORPHOMETRICAL CHARACTERISTICS OF THE GLUTEUS MEDIUS MUSCLE IN HORSES IN PREPARATION FOR JUMPING COMPETITION - PRELIMINARY-STUDY

Biopsies were taken at depth of 3 and 6 cm in the Gluteus medius muscl e 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 mA TPase miofibrillar technique, to determine the fibrillar composition, and with the NADH-TR technique to determine the oxidative capacity. Th e 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 typ e I, IIA, IIB oxidative and IIB non oxidative respectively. The fibril lar composition varied in relation to the depth of the biopsy. Type I and type IIB fibres presented significant percentage differences betwe en 3 and 6 cm. Type IIA was similar in percentage at both depths. Hors es, in the resting period, presented a higher proportion of type IIB f ibres. 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 respective ly. Least diameter was 19, 23 and 28 for fibres type IIA and IIB. Thes e results indicate that the fibrillar composition of the Gluteus mediu s muscle in these horses was different to other breeds.