On an annual basis, the U.S. sow herd experiences a greater than 50 percent replacement rate. That puts the average parity at culling from 3.5 to 3.8 and the number of pigs produced during a sow’s lifetime at less than 40 pigs, says Ken Stalder, Iowa State University animal scientist.

After reviewing available databases, the five most common reasons sows leave the herd are:

  1. Reproductive failure
  2. Feet and leg soundness
  3. Age
  4. Mortality
  5. Post-weaning issues

Reproductive failure is the No. 1 reason for culling sows and Stalder’s recent research shows that while it was cited for 86 percent of the females culled, their reproductive tracts appeared normal upon inspection at harvest. Consequently, this suggests an underlying factor.

Feet and leg soundness is the second-most identifiable reason why sows are culled. Stalder believes that the scope of problems related to soundness is probably underestimated.

“When producers cull sows, they check the box for the problem that they last observed,” he says. “For example, producers check the box ‘did not conceive.’ If the sow was lame or had feet-and-leg-soundness issues, she may not have had sufficient feed intake during lactation. Thus the real reason the female did not return to estrus in a timely manner or did not conceive is that she got too thin resulting from a lack of feed intake caused by structural problems or lameness.”

Pork producers need to ensure they properly identify the cause rather than the latest symptom of a much broader problem. Stalder’s research received National Pork Checkoff funds, and the National Pork Board offers many educational materials on the sow-culling issue. Go to pork.org for items such as a heat-detection poster and a feet-and-leg-soundness poster, and work with employees to improve their livestock management and monitoring skills. The end goal is to help improve sow lifetime productivity.