Molecular approaches to improved pig fertility

Area of Science:

• Animal Genetics
• Reproductive Biology
• Genomics

Background:

• Traditional breeding methods have shown limited success in enhancing pig reproductive traits.
• Advances in molecular genetics and comparative genomics are providing new tools for genetic research in pigs.
• The pig genetic map has expanded significantly, aiding in gene identification and mapping.

Purpose of the Study:

• To identify specific genes and chromosomal regions that influence reproductive performance in pigs.
• To leverage molecular approaches for discovering novel genes affecting traits like litter size and ovulation rate.
• To utilize advances in gene mapping and comparative genomics for improving pig breeding.

Main Methods:

• Candidate gene identification and genomic scans were employed to discover genes influencing reproduction.
• Analysis of the oestrogen receptor locus (ESR) and its association with litter size.
• Genome-wide scans to identify chromosomal regions, such as chromosome 8, potentially harboring genes for reproductive traits.

Main Results:

• The oestrogen receptor locus (ESR) was found to be significantly associated with increased litter size.
• ESR BB homozygotes showed an average increase of 2.3 pigs born alive in first parity compared to AA homozygotes in Chinese pigs.
• Commercial Large White crosses exhibited an average increase of 0.9 pigs per litter due to ESR variations.
• Initial genome scans suggest the presence of genes on chromosome 8 influencing ovulation rate and litter size.

Conclusions:

• Molecular genetics offers powerful tools for identifying genes that control pig reproductive traits.
• The oestrogen receptor gene (ESR) is a key genetic factor for improving litter size in pigs.
• Further research utilizing positional cloning and comparative genomics will likely identify additional genes controlling reproduction.