Unravelling gene switches for the regulation of litter size through the study of swine with high and low prolificacy

Abstract

Between 2012 and 2022, the genetic potential for total number of born piglets increased 2.8 per litter in commercial pigs. Alentejano pigs, from Southern Portugal, have low litter size with an average of 5 piglets providing an opportunity to investigate different gene interactions related with litter size and characterize the biological mechanisms associated with this trait. An experiment was carried out to investigate the effect of breed and season in the gene expression levels of the uterous of Alentejano (AL) and commercial Landrace x Large White gilts at early gestation. Per breed the levels of thyroid hormones and gene expression of uterine tissue collected in three experimental conditions, diestrous (not inseminated), estrous (inseminated, 2 time point of gestation) for two seasons (bi-factorial design) were compared. Results showed that the effect of breed and season was significant, and T3 and T4 serum concentration are higher in AL gilts (p<0.001). The results at gene level showed significant differences allowing to identify candidate genes for further downstream analyses. The identified gene networks reveal connections between the endocrinological and the neurological system. In conclusion, through the study of breeds that have not been intensively for a given trait enables the investigation at molecular level of how genetic variation determines the epistasis and pleiotropic effects on polygenetic traits.