Preliminary Study on Sexual Maturation Pattern of Shenxian Pigs and Molecular Characteristics of Sexual Precocity in Boars

This study aimed to determine the sexual maturation pattern of <i>Shenxian</i> pigs by combining observation, teaser boar testing, and back-pressure methods, and to apply this pattern for early breeding to shorten the generation interval and increase production efficiency. Subsequently, high-throughput transcriptome technology was used to compare gene expression levels in testicular tissues of <i>Shenxian</i> pigs before and after sexual maturity, as well as between sexually mature <i>Shenxian</i> pigs and <i>Shenxian</i> × Large White crossbred pigs. Functional analysis of differentially expressed genes (DEGs) was conducted to screen candidate genes related to sexual maturation and precocity in <i>Shenxian</i> pigs. The results showed that boars reached sexual maturity at an average age of 116 days in winter and 129 days in summer. For sows, the first estrus occurred at 114 days, the second at 134 days, and the third at 154 days in winter; corresponding ages in summer were 125, 144, and 164 days, respectively. The duration of estrus was around 3 days, and the estrus interval was approximately 20 days for both seasons. Comparative trials revealed no significant change in production performance when selection and first mating were conducted at 5 months of age compared to previous practices. Transcriptome sequencing of testicular tissues before and after sexual maturity in <i>Shenxian</i> pigs identified 6016 upregulated genes, primarily associated with reproduction and sperm function, influencing sexual maturation. The comparison between sexually mature <i>Shenxian</i> pigs and crossbred pigs identified 582 upregulated genes, mainly involved in hormone synthesis, affecting the onset of puberty in <i>Shenxian</i> pigs. After intersecting and functionally analyzing the upregulated genes from both sets, SRD5A1 and CYP11B2 were selected as the most likely candidate genes to affect precocious puberty in <i>Shenxian</i> pigs.