Sow longevity is a large component of profitability for commercial swine operations with the sow needing to produce three litters to recover her investment costs. With current culling rates averaging near 50% and mortality rates averaging almost 9%, a small proportion of the sows have the responsibility of making a profit. Past research has shown the primary reasons for culling to be reproductive failure and structural soundness (Chagnon et al., 1991; Stone, 1981), but much of this work is outdated, especially in regards to the genetic background of the sows analyzed. Therefore, a new 20 month study starting in 2005 was conducted on 2,000 commercial sows. This study revealed that the primary culling reasons for sows from current genetic lines has not changed markedly over the years with a large portion of sows being culled for reproductive failure and structural soundness, despite emphasis by genetic companies to improve longevity. The primary reason removal reason listed for sows over parity 5 was “old age” even though most of these sows are still producing at or above herd average. Sows from the group that produced at least 5 parities (parity5+) out performed the young group for number born alive (NBA) when compared at the same parity and had a shorter wean-to-first-service interval than the young group following their first parity. Additional comparisons among sows in the young group revealed that sows that dropped out of production earlier were inferior for reproductive traits when compared to those sows lasting at least four parities. This study shows that sow removal reasons have not changed over the years and sheds new light on differences between sows that drop out of production relatively early and those females that remain productive longer. This study also confirmed that selecting for longevity in sows is not counterproductive to selecting sows for reproductive performance and is actually quite beneficial to reproductive performance.
Available at: http://works.bepress.com/kenneth_stalder/29/