Effect of candidate genes for maternal ability on piglet survival and growth

Our study aimed to test if genes related to maternal ability can be used as genetic markers to improve piglet production. We considered polymorphisms in the oxytocin gene and other loci related to metabolic oxytocin levels and maternal behavior. We hypothesized that genetic variants in these genes can be used to select sows with good mothering ability, expressed as the ability to raise many fast-growing piglets. We identified polymorphisms in candidate genes and used additional closely located known polymorphisms to genotype sows and to test the association of the polymorphisms. Nine genes, oxytocin (OXT), oxytocin receptor (OXTR), mesoderm-specific transcript (MEST), paternally expressed gene 3 (Peg3), growth factor receptor-bound substrate 10 (Grb10), FBJ murine osteosarcoma viral oncogene homolog B (FOSB), cluster of differentiation 38 (CD38), neurohypophyseal hormone arginine vasopressin (AVP) and protein kinase C, gamma (PRKCG) were selected for analysis. We identified four novel single nucleotide polymorphisms (SNP), while 23 SNP identified using sequencing were already reported in a public database. Sows were genotyped using SNP identified using sequencing and from a public database, and a total of 30 out of 65 SNP segregated in the population. We tested the association of 20 markers with traits from up to 164 sows, including number and weight of piglets born and weaned and growth rate of piglets until week 5. Polymorphisms in or close to genes FOSB, PRKCG, Grb10, OXTR, and AVP showed significant associations (after Bonferroni correction, P < 0.00256) with mean birth weight, piglets stillborn of total born and relative weight change of the sow during lactation. We identified some effects (P < 0.05) of SNP close to or within OXT, MEST, FOSB, AVP and PRKCG on number of piglets dead or stillborn from total or live born. Birth weight and piglet growth were slightly (P < 0.05) influenced by polymorphisms in or close to genes Grb10, Peg3 and PRKCG. Two markers in the regions of genes MEST and Grb10 showed an effect (P < 0.05) on the relative fat and weight change of the sow during lactation, respectively. Most of the associations were either identified in the first or second parity, indicating strong differences between the traits across these early parities. Future studies should investigate the correlation between maternal behavior traits and the traits investigated here and test the effect of the investigated loci on behavior in sows. If these genes are associated with favorable maternal behaviors in pigs and if they are useful indicators of the maternal ability, they could be used to identify sows with high genetic ability to raise many fast growing piglets.The survival of piglets is one important measure of successful pig production and the sow plays a major role for the survival of piglets. Selection of maternal lines focusses on maternal ability as it is relevant for piglet survival. We found some associations between candidate gene markers and maternal ability traits. But since the associations were not consistent from the first to the second parity, the markers seem to be less valuable for breeding.