Sow longevity should be the focus for pig producers who aim for maximum profitability, according to Mark Wilson, Ph.D., swine reproductive physiologist at Zinpro Corporation. The goal should be at least four litters per sow, said Wilson — it takes at least three successful parities for a replacement gilt to pay for herself, at which point a producer has covered most or all of the fixed costs for bringing the gilt into the herd.

While cost/benefit analyses show that a goal for gilt introductions should be around 35 percent to keep a swine herd’s parity distribution and returns optimized, current herd replacement rates are approximately 50 percent to 65 percent per year. “Unfortunately, early culling of gilts and young sows sets up a cascade effect within the herd,” said Wilson. Gilt retention rates within a herd can be improved up to 50 percent by implementing changes such as providing larger pen space per pig, utilizing better flooring and feeding a balanced diet. Addressing nutritional needs decreases feed costs, which account for 70 percent of a replacement gilt's cost, according to Wilson.


Lameness is also a factor that needs to be focused on. “Young sows are often culled due to feet and leg problems which hamper reproductive performance and profitability,” said Wilson. “Herd records show lameness accounts for up to 15 percent of total culls through the first parity.” Lameness and its stress on sows also influence reproduction through longer wean-to-estrus intervals, more non-productive sow days, smaller litter size and fewer pigs weaned. Maintaining a proper weight will reduce lameness and the resulting stress, which will raise retention and increase sow longevity.