Comparative analysis of the ovarian transcriptome reveals novel insights into fertility differences in Large White sows

Background Fertility is the most important economic trait in sows, as it is critical for profitability. Considerable phenotypic variation in litter size exists in Large White sows. However, relatively little is known about the underlying molecular and genetic bases. Objective An experiment was conducted to screen key genes that affect the fecundity of pigs during the luteal (L) and follicular phases (F) of the estrous cycle. Methods Eight sows (n = 4 for high fertility sows and n = 4 for low fertility sows) were sacrificed on day 14 (day 1 = first day of estrus) after estrus in the L phase. Another eight sows were slaughtered on day 20 of the estrous cycle in the F phase. Sixteen ovarian tissue samples were collected at the different sacrifice time points. Total RNA extracted was used to construct the library and then sequence on an Illumina HiSeq X10 system. Differentially expressed genes (DEGs) between high and low fertility in Large White sows were identified, and their potential biological functions were analyzed using bioinformatics analysis. Results In total, 457 DEGs (161 up-regulated and 296 down-regulated genes) were detected in the ovarian tissues of the high and low fertility groups in the L phase of the estrous cycle. Furthermore, 475 DEGs (253 up-regulated and 222 down-regulated genes) were identified in the F phase. Twenty-nine DEGs were common to both comparisons. Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that the DEGs were mainly associated with steroid biosynthesis, the Hippo signaling pathway, and lysosomes. Others, such as MSMO1, CYP27B1, and CTSB, were related to reproduction. Conclusion These results will contribute to a better understanding of the individual differences in fertility at the transcriptome level, which may provide useful information to explore new ways to improve fertility in pigs.