Association of BF gene polymorphism with litter size in a commercial pig cross population

Effect of SNPs on Litter Size in Swine

Although sows do not directly enter the market, they play an important role in piglet breeding on farms. They consume large amounts of feed, resulting in a significant environmental burden. Pig farms can increase their income and reduce environmental pollution by increasing the litter size (LS) of swine. PCR-RFLP/SSCP and GWAS are common methods to evaluate single-nucleotide polymorphisms (SNPs) in candidate genes. We conducted a systematic meta-analysis of the effect of SNPs on pig LS. We collected and analysed data published over the past 30 years using traditional and network meta-analyses. Trial sequential analysis (TSA) was used to analyse population data. Gene set enrichment analysis and protein-protein interaction network analysis were used to analyse the GWAS dataset. The results showed that the candidate genes were positively correlated with LS, and defects in PCR-RFLP/SSCP affected the reliability of candidate gene results. However, the genotypes with high and low LSs did not have a significant advantage. Current breeding and management practices for sows should consider increasing the LS while reducing lactation length and minimizing the sows' non-pregnancy period as much as possible.

Allelic to genome wide perspectives of swine genetic variation to litter size and its component traits

Litter size is a complex and sex limited trait that depends on various biological, managemental and environmental factors. Owing to its low heritability it is inefficaciously selected by traditional methods. However, due to higher heritability of ovulation rate and embryo survival, selection based on component traits of litter size is advocated. QTL analysis and candidate gene approach are among the various supplementary/alternate strategies for selection of litter size. QTL analysis is aimed at identifying genomic regions affecting trait of interest significantly. Candidate gene approach necessitates identification of genes potentially affecting the trait. There are various genes that significantly affect litter size and its component traits viz. ESR, LEP, BF, IGFBP, RBP4, PRLR, CTNNAL1, WNT10B, TCF12, DAZ, and RNF4. These genes affect litter size in a complex interacting manner. Lately, genome wide association study (GWAS) have been utilized to unveil the genetic and biological background of litter traits, and elucidate the genes governing litter size. Favorable SNPs in these genes have been identified and offers a scope for inclusion in selection programs thereby increasing breeding efficiency and profit in pigs. The review provides a comprehensive coverage of investigations carried out globally to unravel the genetic variation in litter size and its component traits in pigs, both at allelic and genome wide level. It offers a current perspective on different strategies including the profiling of candidate genes, QTLs, and genome wide association studies as an aid to efficient selection for litter size and its component traits.

Association of BF, RBP4, and ESR2 Genotypes with Litter Size in an Autochthonous Pig Population

The aim of the present study was to determine any potential association of the BF, RBP4, and ESR2 genes with reproduction traits in an autochthonous Greek pig population. The PCR-RFLP methodology was implemented for genotyping purposes of the examined genes. No deviation from the Hardy-Weinberg equilibrium was observed for the examined loci, while the B allele noted to be the more frequent in all analyzed genes. In addition, sows with the AA genotype of BF gene found to produce significantly lower numbers of the total born piglets (TNB) and number of piglets born alive (TNA), while the respective BB genotype significantly exceeded in TNB and NBA traits compared to the other two genotypes (P < 0.001). In the case of RBP4 gene, sows with the AB genotype noted to have significant higher values of TNB and NBA in regard to the respective homozygous genotypes (AA or BB), while the BB genotype showed intermediate results (P < 0.001). There were no statistical differences between the BB genotype and the AB genotype of ESR2 locus in regard to the examined traits. However, a noticeable superiority (P < 0.01) of the BB genotype compared to the homozygous AA genotype, adding almost 2 piglets/litter in TNB and NBA trait, was found.

ABBREVIATIONS

TNB: Total number of born piglets; NBA: Number of piglets born alive.