Sow longevity in the herd
As the saying goes, “it’s not the years in your life, it’s the life in your years”. The same holds true for sows when evaluating their reproductive capabilities and whether they should stay or be culled from the breeding herd. A sow should produce two litters per year.
Elizabeth Hines is an extension swine specialist at Penn State University. She says the term for the number of litters a sow has is “parity” and is a gauge to evaluate her longevity on the farm.
"If I have 2.3 litters per year and I have a parity four animal, she has given me two years-worth of litters. Depending on when I first bred her, if I bred her at six months of age, she should be about two-and-a-half years old," says Hines. "So, we’re looking at parity rather than years for that longevity and productive lifetime of that animal."
Longevity is also highly related to bone density, the skeletal structure of her feet and legs, and the amount of calcium storage.
"That skeletal structure is really important for a reproductively active animal because they pull from that calcium storage routinely. They’re also carrying a lot more weight when she is heavily pregnant prior to farrowing. So, you want an animal that’s going to be able to get up and down more easily," she says. "You also are going to want an animal that’s going to be able to pull calcium out of that calcium storage to make her muscles work and to produce milk."
Hines says on average, the number of piglets a sow can produce starts dropping off after five litters. You will have to decide if it makes more economic sense to keep her or bring in a replacement gilt.