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Sow longevity is an important and costly topic for the U.S. pork industry. Yet it’s difficult to get a handle on how costly it can be.

According to PigChamp data the national sow-parity average at culling is 3.95. Producers ranking in the top 10 percent average 5.8 parities with their culled sows; and producers in the bottom 10 percent average 2.2 parities.

“Assuming average production and marketing rates of a herd, the average farrow-to-finish operation needs at least three parities before a sow has a positive net value, or has paid off your investment,” says Ken Stalder, Iowa State University animal scientist.  “In breed-to-wean operations the breakeven is a little higher, so those producers need even better sow longevity rates.”

Therefore, it’s safe to say the average sow just barely pays for itself. Even if your sow longevity rates are above average, there’s still money to be made from improving your herd’s parity rate. According to Stalder’s calculations, an extra litter beyond the third-parity mark — using a rolling average of hog prices over a five-year period — tallies about a $70 profit.

Here’s another example of how poor sow longevity can cost you money. Say a gilt costs $200, it has 10.2 pigs born alive, and 8.2 pigs are sold out of that litter. Improving the longevity by even 0.10 parities would result in an increase of 23 cents per pig marketed.

“In a 2,500-sow operation that markets 50,000 hogs annually, improving the longevity by 0.10 parities would provide that operation with an additional $11,500 profit,” says Stalder. “This does not include any benefit to the offspring through improved performance in the nursery and grow/finish stages because you have fewer pigs from parity-1 sows.”

Extrapolate that example out to the U.S. sow herd, and Stalder says an increase of 0.10 parities could mean an extra $15 million in profits.

There are several reasons why sow longevity is so costly. First, there’s the cost of replacement gilts, and the fact that any sow culled before parity-3 is still costing you money. There also are productivity losses from the offspring of parity-1 sows, so the fewer of those sows in your herd the better.

Because the young sow’s colostrum may not have the same immunity levels as colostrum from older sows, offspring of parity-1 sows don’t receive as much protection from pathogens. As a result, those pigs don’t have as strong a health status as other pigs, and they grow slower. This can create uniformity problems as pigs head for market. It’s one reason why many large production units practice parity segregation, with offspring of parity-1 sows housed in different rooms or different buildings than pigs from older sows.

“Sows farrowing between parity-2 and parity-5 tend to have the best performing progeny. Eventually sows start to become less productive again,” says John Deen, DVM, University of Minnesota. “The lower progeny productivity, especially from parity-1 animals, can cost as much as $2 per pig.”

Deen says a sound goal is for 80 percent of gilts placed into a herd to reach parity-2. That should maintain an acceptably low number of parity-1 sows and their lower-performing progeny.

There are two main reasons why sows are culled prematurely: reproductive failure and foot-and-leg issues. Stalder says 35 percent of sows culled in the parity-1 or parity-2 stage are due to reproductive failure, while the number culled because of foot-and-leg problems is about 10 percent to 15 percent.

“Examples of reproductive failures could be the sow’s failure to cycle after weaning, failure to conceive or being found ‘not in pig’, which is the worst scenario because the sow often goes through all or most of the cycle before this is discovered,” says Stalder.

But Deen suggests that exercising a little patience as you cull sows could be beneficial. “Producers need to make an overall effort to increase farrowing rates, and avoid culling simply on low rates. A lot of the problems in low-performing herds are human errors rather than sow problems; so you can’t cull your way into a higher farrowing rate.”

There are a couple exceptions where Deen believes parity-1 sows can be culled for reproductive failure:

  • When you simply cannot detect the animal’s estrus.
  • Very low litter size — such as two or three pigs per litter.

It’s true that sow longevity is a bigger issue today than in the past, which begs the question “what is causing the sow longevity decline?”

Deen isn’t so sure that sows today are really performing worse. Rather, he believes production expectations are higher for sows than in the past, and producers are anxious to cull sows performing below those expectations.

Sow mortality, which usually occurs shortly before or after farrowing, has been trending upward. Less individual attention to the sow or perhaps a less experienced workforce could be contributors.

It’s important to pay close attention to the animal’s feed intake and health, as well as the herd’s health status before and after farrowing. Again, Deen emphasises not getting overly anxious to cull based on reproductive failures, especially when it comes to parity-1 sows.

“There’s been more emphasis on lean, heavily muscled animals, which has limited the sows’ ability to adapt,” says Mark Boggess, director of animal science, National Pork Board. “Also, the industry’s push toward heavy carcass weights has created increasingly larger sows. That can lead to more leg problems for older animals in the breeding herd.”

“Sow longevity is influenced by genetics, but its heritability is generally low, like a reproductive trait, with estimates between 0.05 percent to 0.19 percent heritability,” says Stalder. “That means selection for sow longevity is possible, but improvements would likely be slow.”

That leaves management as your best opportunity to influence the outcome. There are, in fact, plenty of management options to improve sow longevity.

“One major point is that we don’t develop gilts correctly. Too many gilts are rushed through isolation and acclimatization stages because there are holes in the breeding schedule,” says Stalder. “I would argue that better planning could prevent this. Sow longevity also could improve a lot if gilts are fed correctly in the developmental stage, and have adequate boar exposure.”

Stalder suggests getting replacement gilts off of finishing diets, and catering to their future reproductive nutritional needs. For more specifics on replacement-gilt diets, go to

As for boar exposure, opinions vary on when to begin, but Stalder says, starting when gilts are around 170 days old should be sufficient. He recommends exposing gilts to boars for 15 to 20 minutes at a time, twice a day. This means fence-line, nose-to-nose contact.

Problems with sow longevity will not go away easily. Improvements require attention and hard work from you and your support system — researchers, veterinarians, nutritionists, geneticists and the like. The industry has made finding those answers more of a priority today. “The National Pork Board has identified some of the issues within gilt development and made them research priorities for 2005,” says Boggess. “Educating producers and employees about the importance of looking for things like even toes and leg angulations when selecting replacement gilts is a start. Continuing to improve stockmanship skills would likely improve sow longevity and other aspects considerably.”

While sow longevity is an issue that sorts out producers in terms of competitiveness and profitability, it’s also an issue that will challenge the U.S. pork industry at the international level. After all, it’s a factor that influences who is and who remains a low-cost producer to the world market.