More is better until it’s not. In the past 20 years, live born per litter has increased by about four pigs for the average pork producer. Abigail Jenkins, director of nutrition for Tosh Farms in Henry, Tenn., says this may sound like a great thing at first. The problem is that even though more pigs are hitting the ground, functional teat count of the sow has not increased at the same rate as the change in live born.
“For a long time, we’ve been taught that you load sows up to the same number of pigs as she has teats,” Jenkins explained at the Allen D. Leman Swine Conference. “However, as productivity has improved, producers are being faced with the challenge of a hyperprolific sow who has more pigs than teats. What do we do with these additional pigs?”
Jenkins says there are few ways to handle extra pigs – artificial rearing, fostering to nurse sows (sows who have weaned a litter of their own and are pulled back into a room of newly farrowed pigs to support those extra piglets), or allowing the sow to nurse more pigs than teats. All of these options pose their own set of negative consequences on piglet livability.
“Artificial rearing isn’t always practical and comes with some drawbacks, so the most commonly used strategy for more pigs than teats is nurse sows,” Jenkins says.
With nurse sows, however, you can’t get additional colostrum into the piglets because the sow is producing mature milk at this point. The piglet’s chance of getting colostrum stops at cross fostering.
“We also have to consider the increased risk of disease transmission because we’re moving that sow, typically from a room of weaned pigs that may have some other diseases or illnesses, into a room of newborn pigs that are born severely immunocompromised,” Jenkins says.
It also requires open crates to move the nurse sows into, which means the producer has to decrease breeding targets to allow for space.
How Does This Affect Mom?
If producers let sows nurse more pigs than teats, how would it impact key performance indicators? How will that impact pre-weaning mortality? What about subsequent sow reproductive performance and litter weaning weight? During a project as a research assistant at Kansas State University, Jenkins set out to answer these questions using 1,005 sows and their litters in a commercial sow farm trial in the panhandle of Texas.
In this study, a protocol evaluated one less pig than functional teat count, the same number of pigs as functional teat count, one more pig than functional teat count, or two more pigs than functional teat count.
She discovered that the optimal litter size relative to functional teat count depends on the performance measure of greatest interest. Sows nursing a litter size below functional teat count have lower pre-weaning mortality and sow body weight loss and greater pig weaning weights. However, as litter size increases relative to functional teat count, overall farm throughput improves by increasing pigs weaned per litter, litter weaning weight, and pigs weaned/sow/year.
“The sows did lose more body weight over lactation when we increased litter size relative to functional teat count,” Jenkins says. “In addition, they lost more backfat and they lost greater caliper units as we increased that litter size relative to functional teat count – that wasn’t a surprise to us. One of the things that was surprising was that while those sows did lose more body weight and more body condition as we increased litter size, the differences between sows loaded at one less pig than functional teat count to sows loaded at two more pigs at functional teat count was relatively small.”
Just taking sow body weight as an example, they saw about a 10-pound difference in change in body weight over lactation across the four treatments. In the grand scheme of things, she says it’s really not as big of a difference as they expected.
How Does Functional Teat Count Affect Pig Growth?
From a litter standpoint, the results showed an increase in combined removals and mortality as they increased the number of pigs nursing relative to teat count. But that increase happened at a diminishing rate, she explains. They still saw an increase in litter size at weaning as they increased the number of pigs nursing, even though there was an increase in removals and mortality.
From a litter weight perspective, the results showed an increase in litter weight at weaning as the number of pigs nursing increases. But, when you consider the average piglet body weight at weaning, there was a decrease in piglet body weight at weaning as the number of pigs nursing increased.
“That’s one of the things that we expected to see,” she says. “Because you have more competition at the underline, you would expect those pigs to gain less weight over lactation. But it’s important to grasp that across all four of our treatments, these sows, on average, were still weaning pigs that were greater than 13 pounds. Even though the plus two sows weaned a smaller piglet, they were still weaning a good size piglet.”
Jenkins was particularly interested in the proportion of the litter weaned in each body weight category. She was concerned about the smallest body weight groups and wanted to be sure they weren’t just weaning more small pigs.
“When we looked at those differences in the proportion of the litter that’s weaned in each body weight category, what we saw is that in our minus one sows, they did wean a higher proportion of pigs that were in the heaviest body weight group, pigs greater than 16 pounds,” she says. “But when you looked at the proportions of the sows at and above functional teat count, there really wasn’t any big differences in the proportion of the litter weaned in each body weight category. That tells us that we didn’t just increase the proportion of those small pigs, we kept the body weight distribution of the litters similar across our treatments.”
Subsequent Sow Performance
Some of the most important data collected was the subsequent sow performance. At the time this trial was conducted, there wasn’t much data available that looked at things like the percentage of sows that were bred by day 7, Jenkins points out.
“When we looked at those results, we didn’t see any significant differences in the percentage of sows bred by day 7 post wean or the subsequent farrowing rate,” she says.
They did see an increase in the subsequent live born of these sows. The sows that were nursing two more pigs than functional teat count on average had 1.2 more live born pigs in that next farrowing compared to the sows that were nursing at one less pig than functional teat count.
“I did have to show Dr. Tokach so he could double check, because we were both a little surprised by it,” Jenkins says. “As we increase the number of pigs nursing relative to functional teat count, this data would tell us that not only did we not hurt subsequent production, but actually some parameters show an improvement in subsequent sow performance and production when we increase the number of pigs nursing relative to teat count.”
One of the last things they did in this study was estimate the pigs weaned per sow per year, an important KPI for producers across the U.S.
“We estimate that there would be a difference of 3.5 pigs between our sows nursing at two more pigs than functional teat count and our sows nursing at one less pig than functional teat count,” Jenkins says. “That was a really large difference in pigs weaned per sow per year, and that has to do with that increase in litter size at weaning as we increase the number of pigs nursing.”
A video summary of functional teat count management can be found here.
