MEAN FIBER AREA OF SEMI-TENDINOSUS, DIAPHRAGM AND PECTORALIS TRANSVERSUS MUSCLES IN DIFFERING TYPES OF HORSE AND DOG

  • 1 January 1978
    • journal article
    • research article
    • Vol. 127  (OCT) , 403-414
Abstract
The thoroughbred horse and greyhound are recognized as examples of fleetness within their respective species. The possibility that there may be differences in muscle fiber areas between athletes (thoroughbreds and greyhounds) and other members of their species as adults and during growth is investigated. Samples from 3 muscles - m. [musculus] semitendinosus, m. diaphragma and m. pectoralis transversus - were removed immediately post-mortem from 66 horses and 59 dogs of various breeds and ages. Muscle samples were deep frozen, cut on a cryostat and the fresh frozen sections stained with hematoxylin. Mean fiber areas were estimated by back projecting stained sections on to a glass screen and counting the numbers of fibers within a known area. As adults the mean area of fibers in m. semitendinosus and m. diaphragma is greater in athletes than in the control animals, but there is no difference in the pectoralis transversus mean area between the 2 types of animal within each species. During growth the mean fiber areas of the 3 muscles increase to a greater extent in athletes than in non-athletes. No differences due to sex were detected and detraining adult greyhounds did not significantly alter fiber area. Although the mean fiber area from samples of horse muscles were significantly larger than those in corresponding samples from dog muscles the difference is proportionately less than that of their live wt.