Estudo da miogênese fetal de suínos em diferentes períodos gestacionais

Abstract

This experiment was conducted to evaluate the effects of gender and fetus position within the uterus over swine myogenesis, at different gestational ages. We used fifteen primiparous sows, divided into three groups according to gestational age at slaughter: 50, 80, and 106 days. The experimental design was completely randomized, in a 2 x 3 factorial design - two genders (male and female) x three uterine regions (apex, middle, base). After slaughter and removal of the reproductive tract, each uterine horn was divided into three segments of equal length: apex region, closest to the ovary; base region, closest to the uterine body; and the middle region, located between the above. The fetuses were weighed, identified and open longitudinally in order to harvest the semitendinosus muscle and, later, perform morphological analysis. After 50 days of pregnancy, male fetuses showed higher (P <0.05) weight when compared with female, in addition to presenting tendency for greater primary fiber area. The number of primary fibers was negatively correlated with the number of fetuses within the uterus. After 80 days, fetuses belonging to the base region had lower (P < 0.05) secondary muscle fiber area when compared to fetuses from the apex. The ratio of secondary: primary fibers was positively correlated with weight. In conclusion, gender may influence muscle development in fetuses at early development stages, and the position in the uterus affects the development of secondary muscle fibers. Fetuses of the base region presented the lowest development.