Alterações estruturais e perfil da expressão gênica durante o desenvolvimento muscular esquelético pós-natal em suínos de diferentes pesos ao nascimento

Abstract

Low birth weight piglets have compromised postnatal growth due to impaired muscle accretion, which may affect meat quality in these animals. The present study investigated skeletal muscle development in different birth weight female pigs by evaluating histomorphometrical changes in muscle fibers, the expression of genes related to myogenesis, adipogenesis and growth, as well as the quantification of different myofiber types. Sixty pairs of littermate gilts were selected: one piglet with high (HW) and the other with low birth weight (LW) within a litter. Three sub-sets of 20 pairs of female littermates from each experimental group were obtained after selection: one sub-set was euthanized at birth, one at 100 days (-d) and another at 150-d of age. HW gilts were observed to have greater body weights than their LW counterparts at all ages evaluated (P < 0.05). In addition, LW newborn females showed higher brain to liver weight ratio, providing evidence of intrauterine growth restriction (P < 0.05). Even though muscle fibers were larger at birth in the HW group, they presented similar diameters at 100-d and 150-d old. The percentage of myosine heavy chain (MHC)-I myofibers was higher in LW females (P < 0.05) at birth, however in older gilts (150-d), HW showed higher percentage of MHCII-x fibers (P < 0.05). The mRNA levels of myogenic, adipogenic and growth-related genes showed similar patterns of gene expression in the semitendinosus muscle of the three ages evaluated. Hence, the myofibers structural changes presented herein may be mediated by gene expression alterations during the embryonic phase, which may predetermine the reported relationship between muscle growth, postnatal growth performance and meat quality.