The administration of porcine somatotropin (pST) to pregnant sows duri
ng early gestation (day 10 to 24) induced the formation of significant
ly more muscle fibres in the semitendinosus muscle of the fetuses, rep
resenting a higher growth capacity of skeletal muscle. The pST-treatme
nt during late pregnancy (day 80 to 94) accelerated the development of
the fetus resulting in higher body weights and advanced stage of matu
rity at birth.