The fat mass and obesity-associated gene (FTO) has previously been associated with human body mass index and porcine intramuscular fat content. In this study, the potential alternative splicing pattern of the FTO gene was investigated, and three novel splice variants were identified in Large White and indigenous Chinese Tibetan pigs. To explore the molecular effect of the FTO gene on the fat deposition caused by castration, 40 paired full-sibling male pigs were divided into intact and castrated groups, and the trait data showed that abdominal fat weight, percentage of abdominal fat weight, and backfat thickness in the intact group were significantly lower than in the castrated group (p < 0.05). FTO mRNA expression in the hypothalamus was significantly increased in the castrated group compared with the intact group (p < 0.05), but was not different in the abdominal fat or backfat tissues. Moreover, the relative expression of the FTO gene was shown to have a higher level in the hypothalamus when compared with expression in the fat tissues (p < 0.05). Our results suggest that there are different patterns of alternative splicing and FTO expression among pig breeds. This study will provide clues for obtaining a better understanding of the porcine FTO gene function.