Genetics/Reproduction

Genetic Markers Targeted for Sow Longevity

Preliminary research at Iowa State University (ISU) is targeting genes that are associated with sow longevity. These genes may not only have a positive effect for the number of litters a sow produces, but some may also have a positive impact on litter size.

Sow longevity is of great economic importance to the bottom line of swine production. High sow mortality has contributed to concerns over animal welfare and negatively impacted staff morale. High sow culling or mortality rates are forcing sow dropout rates higher, before many females reach their most productive parities, and before investment cost of females can be recovered.

Realizing that genetic mechanisms have a major role to play in controlling sow longevity, ISU has teamed with PIC to focus on identification of these key genes.

Scientists have identified pathways and genes in model organisms, such as mice and flies, which have shown longer life spans. To determine if the same pathways or genes are involved in sow longevity, scientists are examining information from those model organisms.

Two sow groups have been used as research models in preliminary studies. The first group consists of about 1,000 commercial sows, with almost half having less than five parities, and the rest having more than eight parities. The second population consists of more than 200 sires, where complete lifetime production records were recorded on their daughters (minimum of 10 daughters/sire). Genotypes from each gene were analyzed for association with sow longevity in both populations.

Three of 10 candidate genes investigated were identified as possessing significant effects on sow longevity. The effects of these genes ranged from having a beneficial effect of 0.2 to over 2.0 more litters, depending on the farm and population of animals analyzed. One of these genes also had a beneficial effect on litter size, suggesting that if selection for this particular gene is made, then the producer can benefit from sows having more litters and also having more live pigs/litter.

If producers are able to select sows that raise more litters, they will purchase fewer replacement females. This will translate into lower replacement costs, improved production due to more sows being in peak production, improved herd health with fewer introductions, and most importantly, better producer returns.

For a farrow-to-finish producer, an increase in average parities/sow lifetime of just a tenth of a parity (i.e. going from 3.4 to 3.5 average parities/sow) calculates into a benefit of 23¢ for every market hog sold. Likewise, a farrow-to-wean producer can realize a return of 13¢ for every pig sold for the same increase of 0.1 average parities.

Further research on different and larger pig populations will be necessary before these genes can be used for selection in swine production. But these early results hold promise that advances in sow longevity will be achievable in the near future.

Researchers: Max Rothschild, professor; and Benny Mote, graduate assistant, Iowa State University. Phone Rothschild at (515) 294-6202; fax (515) 294-2401; or e-mail mfrothsc@iastate.edu.