Whole-Genome Association Analyses for Lifetime Reproductive Traits in the Pig

Genes associated with litter size were found to be expressed in reproductive tissues and those for fertility traits were found to be linked to fat deposition, according to researchers at Iowa State University.

31 August 2011

3 minute read

S.K. Onteru and colleagues at the Department of Animal Science and Center for Integrated Animal Genomics at Iowa State University have studied the pig genome and its associations with lifetime reproductive performance.

Profits for commercial pork producers vary in part because of sow productivity or sow productive life (SPL) and replacement costs, they explain in the introduction to their paper published in the Journal of Animal Science. During the last decade, culling rates of sows have increased to more than 50 per cent in the United States. Both SPL and culling rates are influenced by genetic and non-genetic factors, they added.

The Iowa researchers conducted a whole-genome association study for pig lifetime reproductive traits, including lifetime total number born (LTNB), lifetime number born alive (LNBA), removal parity and the ratio between lifetime non-productive days and herd life.

The proportion of phenotypic variance explained by markers was 0.15 for LTNB and LNBA, 0.12 for removal parity, and 0.06 for the ratio between lifetime non-productive days and herd life.

Several informative QTL regions (e.g. 14 QTL regions for LTNB) and genes within the regions (e.g. SLC22A18 on SSC2 for LTNB) were associated with lifetime reproductive traits in this study, according to Onteru and co-authors.

Genes associated with LTNB and LNBA were similar, reflecting the high genetic correlation (0.99 ± 0.003) between these traits.

Functional annotation revealed that many genes at the associated regions are expressed in reproductive tissues. For instance, the SLC22A18 gene on SSC2 associated with LTNB has been shown to be expressed in the placenta of mice.

Many of the QTL regions showing associations coincided with previously identified QTL for fat deposition. This reinforces the role of fat regulation for lifetime reproductive traits.

Overall, this whole-genome association study provides a list of genomic locations and markers associated with pig lifetime reproductive traits that could be considered for SPL in future studies, concluded the Iowa team.

Reference

Onteru, S.K., B. Fan, M.T. Nikkilä, D.J. Garrick, K.J. Stalder and M.F. Rothschild. 2011. Whole-genome association analyses for lifetime reproductive traits in the pig. Journal of Animal Science, 89 (4):988-995. doi: 10.2527/jas.2010-3236