Too many sows are failing to cycle or conceive and are forced to leave the breeding herd early.

Ask fellow producers to compile a list of production concerns and sow longevity would be near the top. Culling sows early has become a major problem in the industry costing U.S. producers millions of dollars.

Sow longevity is a growing concern partly because improvements in recordkeeping have illustrated the decline. Also, more of you are investing in high-priced gilts with more genetic potential, making sow culling a more sensitive topic, says Rodney Goodwin, the National Pork Producers Council’s research director.

First, there’s the cost of replacing the gilt, which means development costs will be spread over less parities. Also, since most females don’t have as many pigs in their first and second litters as they do later on, you will produce fewer pigs overall if you have to keep replacing sows.

“A big factor that many people don’t consider is the increased risk of disease when you frequently introduce replacement animals into the breeding herd,” says Ken Stalder, University of Tennessee swine specialist.

Stalder uses a Gilt Calculator modeling program to figure out when a gilt shows a return on the initial investment. The Gilt calculator is free and can be obtained by calling Stalder at (901) 425-4717.

Stalder’s data shows that after the third parity the sow has paid for itself and the return on investment grows by about $70 per additional parity, depending on your profitability. Add that up over a 500-sow herd and it totals an additional $35,000 for each extra parity.

The average parity length is currently 3.5 litters, according to PigChamp data. Stalder believes that could be taken at least one parity further, noting that the top 10 percent of producers using PigChamp get an average 4.9 parities out of a sow. So there is room for improvement. Stalder considers an annual culling rate of 50 percent to be too high.

In the Maternal-Line Genetics Program, an NPPC study that tested 3,559 female hogs from six different genetic lines, Goodwin saw first-hand the potential for fertility and longevity.

Average totals for a 25-gilt cohort over a four-parity study was 60 litters out of a possible 100. However, genetic lines with superior reproductive traits averaged 80 litters and some cohorts reached 90 litters.
Fertility problems are the biggest reasons why a sow is culled. Most sows that are culled either fail to cycle or fail to conceive in one of its first two parity periods.
“Sow longevity is a formula that centers on the ability to conceive,” says Goodwin. “If an animal doesn’t even have a litter that hurts longevity badly.”

Theories abound as to what is causing the increased early culling, but it is probably a combination of things.

For one, pigs grow faster today and gilts often enter the breeding herd at 5.5 months. “We’ve had relatively young sows that are trying to grow and produce a litter at the same time. They usually don’t eat enough after lactation, so nutrients are pulled from their reserves,” says Stalder. “In addition some of the problem may be traced to inadequate gilt development before breeding begins. And then there’s the possibility that we may have taken leanness too far.”

Seedstock suppliers have become more concerned with sow longevity, but are still concerned with the end product as well. Every trait you add to the genetic equation slows down the selection process, says Goodwin. Balancing carcass and production traits with reproductive traits has always been a challenge. In the end, the practice is producer-dependant, says Goodwin.

“You need to model your replacement gilt costs and hog marketing program to determine how much emphasis you should place on sow longevity vs. growth traits like feed efficiency, leanness or other factors for your particular operation,” says Goodwin.
Stalder agrees noting that most packers aren’t paying high premiums for the ultra-lean hogs anymore, so sacrificing appetite for leanness in the breeding herd should be avoided.

Management aspects like more accurate heat detection, gilt development or feed additives may play a larger role in solving the sow longevity problem than genetics, because longevity is a lowly heritable trait.

“Estimates show that genetics control about 10 percent to 15 percent of sow longevity, but the rest is influenced by management and environmental factors. That’s typical with most reproductive traits,” says Goodwin. “There’s certainly a genetic component, but it’s slow and costly and you don’t make selections until the sow is quite old.”

Goodwin predicts sow longevity may be improved as a corollary trait when you select for traits to increase fertility and to reach puberty at a younger age.

Stalder suggests renewing basic management skills like feeding sows in gestation to fit their body condition as a place to start. “If you normally feed 4 or 5 pounds of feed per day you may need to increase to 6 or 7 pounds per day, but you need to watch individual sows and feed to their body type,” says Stalder. “You can’t just set the dials and walk away.”

Stalder also recommends keeping lactating sows cool, making sure to clean the feeders often to prevent mold and feed refusal. He also recommends keeping as few sows in a pen as possible during gestation – no more than eight sows in any pen.

Resolving the problem of having to cull sows too early is a complex issue. Every possible solution has its own downside. For now, paying attention to heat detection, seeing that sows get as much feed in the gestation period as possible and other management practices remain your best bet. But keeping an eye on new research and technologies is worth your time and attention, because they will continue to provide additional clues to sow longevity.