With average litter sizes rising much faster than functional teat counts, pork producers are constantly looking for creative ways to keep extra piglets thriving. While traditional nurse-sow systems have been the standard fallback, recent commercial trials reveal that letting sows over-nurse, leveraging “opportunity sows” for smaller pigs, and utilizing computerized precision feeding can dramatically boost herd performance without dragging down subsequent reproductive rates.
Can Sows Nurse More Pigs Than Teats?
More is better, until it’s not. In the past 20 years, live born per litter has risen by about four pigs for the average producer. This may sound great, but while more pigs are hitting the ground, functional teat count of the sow has not risen at the same rate as the change in live born, says Abigail Jenkins, director of nutrition for Tosh Farms in Henry, Tenn.
“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?” she asks.
Jenkins says ways to handle extra pigs include artificial rearing, fostering to nurse sows (those that have weaned a litter of their own and are pulled back into a room of newly farrowed pigs to support extra piglets) or allowing the sow to nurse more pigs than teats. All these options pose a 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, additional colostrum can’t get 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 affect key performance indicators (KPIs)? How would it impact preweaning mortality? What about subsequent sow reproductive performance and litter weaning weight? During a project as a research assistant at Kansas State University, Jenkins sought answers using 1,005 sows and their litters in a commercial sow farm trial in the Texas Panhandle.
In this study, a protocol evaluated one fewer pig than functional teat count, the same number of pigs as functional teat count, one more pig than functional teat count and 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 preweaning mortality and sow body weight loss and greater pig weaning weights. But 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.”
Taking sow body weight as an example, they saw about a 10-lb. difference in change over lactation across the four treatments; that’s really not as big of a difference as they expected, she says.
Effect on 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; that increase happened at a diminishing rate, Jenkins 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.
The results showed an increase in litter weight at weaning as the number of pigs nursing increased. But when considering 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 lb. Even though the plus two sows weaned a smaller piglet, they were still weaning a good-size piglet.”
Sow Performance
Some important data was collected about subsequent sow performance.
“We didn’t see any significant differences in the percentage of sows bred by Day 7 postwean or the subsequent farrowing rate,” Jenkins says.
They saw an increase in the subsequent live born of these sows. Sows 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 nursing at one fewer pig than functional teat count.
“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,” Jenkins says.
In this study, they also estimated pigs weaned per sow per year.
“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.”
When ‘Negative’ Nurse Sows Become an Opportunity
When hyperprolific sows produce more pigs than teats, there may be better ways to manage those large litters. Jenkins completed a study while at Kansas State University comparing the impact of sows nursing pigs above, at and below functional teat count.
She discovered 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 preweaning 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 Need for Nurse Sows
Using the average pigs born alive and the average functional teat count at this sow farm at the time this trial was conducted, Jenkins determined how many nurse sows would be needed to handle the extra pigs because the live born was greater than the functional teat count. If the farm loaded 250 sows at each of the four treatments, this is what she found:
- If the sows were loaded in groups of 250, at one less pig than functional teat count, 24 nurse sows would be needed for the extra pigs.
- If the sows were loaded at functional teat count, seven nurse sows would be needed.
- If the sows were loaded at greater than functional teat count (plus one or plus two), it actually resulted in negative nurse sows needed.
“Intuitively, this doesn’t make a lot of sense,” Jenkins points out. “The explanation behind that is those sows are ones that we have cleared off her litter and put her pigs onto other sows to get them up to either plus one or plus two. Then, we have these sows that have just farrowed that now have an open crate that we can utilize as tools in our farrowing rooms. These sows can be used as what I refer to as opportunity sows.”
What is an Opportunity Sow?
Opportunity sows take pigs that are less than 2 lb. Jenkins says the key is the pigs are small, but they must be viable. Opportunity sows used for this should be younger parity but not gilts. They should be sows with proven production history. They need smaller-sized teats so the smaller piglets can nurse easily.
“The opportunity litters are going to be large — 15 or more pigs,” she says. “Essentially, this concentrates all your small pigs into a few litters, so you can have more in-depth care for these small pigs and less competition.”
Fall-Behind Litters
Another way to use these negative nurse sows, or opportunity sows, is in fall-behind litters — pigs removed from their initial litters because of failure to thrive or because they are not doing well nursing on their current sow.
“It’s important those pigs get removed early, whenever those signs are first being seen,” Jenkins explains. “The earlier the intervention, the greater the chance that you can really make a difference.”
Though some people would use a traditional nurse sow for a fall-behind litter, she says the newly farrowed sows actually make ideal sows for fall-behind litters for two reasons:
- These sows are still going to produce a little colostrum or they’re going to produce transition milk, both of which are higher in fat and protein content. It allows you to get more nutrients into those fall-behind pigs.
- Newly farrowed sows allow litters to nurse more frequently than a sow that just weaned a litter of her own.
“When you combine having milk that is higher nutrient content and a sow that’s going to allow those pigs to nurse more frequently, your chances that those fall-behind pigs recoup faster is much better,” Jenkins says.
Precision Feeding During Lactation
Does precision feeding sows during lactation pencil out? Mike Tokach, University Distinguished Professor and Extension specialist at Kansas State University, says that’s a key question for producers to consider when it comes to feeding sows.
Most producers focus on having fresh feed in front of sows so they can eat whenever they want to maximize consumption. When it comes to precision feeding a sow, Tokach says it’s important to know how much the sow is eating, her level of milk production, how many pigs she is nursing and approximately what the litter gained compared to previous groups on the farm.
“This allows the producer to know how much milk she’s producing per day based on her litter size, and that tells us
the amino acids she needs,” Tokach explains. “Based on her level of feed intake, we can adjust what diet we need to get the right percentage lysine or the right percentage of each of the amino acids in the diet to be able to blend those together to meet her requirements.”
Precision Feeding Results
Mikayla Spinler, a graduate research assistant, led two studies at the K-State Research Farm and a large field study at Brenneman Pork.
In the first trial, Spinler used three models. The first included a single diet fed all the way through. The second was based on exactly what the NRC says sows need. The third fed the sows like the European model, INRA, says sows need to be fed.
“Both the NRC model and INRA model underfed lysine to the sows by about 20%,” Tokach explains.
In the second study, Spinler used the NRC model and increased its target by 20%. With that approach, the sows had the same performance whether they had one single diet or the NRC model plus 20% tailored to their individual needs.
In the third trial at Brenneman Pork, Spinler wanted to find out if she could achieve the same results with a large number of sows on a commercial swine farm. Tokach says she found the same thing as her second study.
They could achieve the same performance with fewer nutrients because they targeted exactly what the sow needs daily.
Targeted Nutrition
In Spinler’s trial, the sows fed the individual diet that met the needs of all the sows, consumed about 80 g of lysine per day. The precision-fed sows consumed just over 60 g of lysine daily.
“When you think about that difference and the fact that they had the same performance, the difference is basically wastage of nutrients,” Tokach says. “That reduction in cost is one of the big advantages. For many producers, nitrogen excretion and phosphorus excretion are not as critical as it is for some of the European producers where nitrogen and phosphorus excretion limits the number of sows they can have on the land.”
He also notes that precision feeding allows producers to factor in the effect of parity. First-parity sows eat about 20% less feed than an older-parity sow. Though first parity sows produce a little less milk, he points out that it is not that much less. Because of this, they need a higher nutrient-dense diet in most situations than an older parity sow for milk production.
Is It Worth the Cost?
“Precision feeding now uses a computerized system that will provide a targeted amount of total feed that sows can be fed at any one time,” Tokach points out.
Some of these electronic feeding systems can blend two diets together. As the sow progresses through lactation, these systems allow producers to use more of one diet and less of the other to match the curve to meet amino acid requirements as they change during lactation. Tokach says the systems can be complex or simple in terms of the curve setup for the sows.
Ultimately, producers evaluating new construction or planning renovations to lactation rooms should determine the technology cost and the return-on-investment time frame, he says.
On-farm employees must be trained and develop the needed skills of utilizing the lactation feeding technology equipment to fully capture the benefits of more accurate feeding of all females in the herd.
