Muscle Growth in the Fetal and Neonatal Pig

Abstract

Growth of the musculature and skeleton was studied in fetal and neonatal pigs. Muscle growth (dry weights) was related to allometric growth of the whole body as judged by linear skeletal measurements. The relatively large size of the limbs at birth was due to their rapid fetal growth. The growth rates of eight representative muscles of the head and limbs decreased during the fetal and neonatal periods; only the growth rate of the longissimus showed a marked postnatal increase. It was estimated that myofiber hyperplasia was complete by 70 days gestation. Evidence was found to suggest that, during fetal and neonatal periods, intrafascicularly terminating myofibers grow at a faster rate than completely tendinously inserted myofibers.