# Effect of SNPs on Litter Size in Swine

## TL;DR

This paper investigates how genetic variations (SNPs) affect pig litter size and suggests ways to improve breeding practices for better productivity and sustainability.

## Contribution

The study provides a meta-analysis of SNPs' effects on pig litter size and evaluates the reliability of current genetic evaluation methods.

## Key findings

- Candidate genes are positively correlated with increased pig litter size.
- PCR-RFLP/SSCP defects reduce the reliability of candidate gene results.
- Genotypes with high or low litter sizes do not show significant advantages.

## Abstract

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.