MUSCLE DEVELOPMENT IN LARGE AND SMALL PIG FETUSES

  • 1 January 1983
    • journal article
    • research article
    • Vol. 137  (SEP) , 235-245
Abstract
The largest and smallest littermates were chosen by weight from [pig] litters of 38 days'' gestation to 1 day post partum. Complete frozen sections of the semitendinosus muscle were used to provide a qualitative and quantitative account of the development of the primary and secondary generations of muscle fibers. The time of formation of primary and secondary fibers, and the numbers of primary fibers formed, were the same in both large and small littermates. The number of secondary fibers formed, however, was lower in the smaller fetuses and resulted in there being a 17% difference in total fiber number at birth. Primary fibers in small fetuses were smaller, due to the smaller central myofibril-free region. This small size may have restricted the available surface area for secondary fiber formation. Fiber hyperplasia was found to cease between 85 and 95 days'' gestation, and so the fiber number difference is likely to be permanent.