Effects of Castration on Androgen Receptor, IGF-I Ea, MGF and Myostatin Gene Expression in Skeletal Muscles of Male Pigs

Castration of male pig produces significant negative effects on skeletal muscle development. The androgen receptor (AR), two splice variants of insulin-like growth factor-I (IGF-I Ea and MGF) and the myostatin gene may play important roles in this process. In the present study, the expression of AR, IGF-I Ea, MGF and myostatin genes in three skeletal muscles, the brachialis, longissimus and semitendinosus, were studied using real-time quantitative RT-PCR. Our experimental design used 14 pairs of male Landrace sire×Yorkshire dam piglets. The two piglets in each pair were full sibs, one of which was castrated at 21 d of age; the other remained intact. The study group was divided into subgroups of equal size. Animals in the first subgroup were slaughtered at 147 d and those of the second at 210 d of age. Carcass weight and lean meat yield were similar between boars and barrows at 147 d of age (p> 0.05), whereas barrows had lower carcass weight and less lean meat yield at 210 d of age (p 0.05). These results suggest that the down-regulation of AR, IGF-I Ea and MGF gene expression following castration helps to explain the negative effect of castration on skeletal muscle development.