Gilt selection and management are often overlooked as critical drivers of sow lifetime productivity.

When thinking about farm productivity there are many factors across each production stage that influence the outcome. Sows in the farrowing room get a lot of attention and rightly so. It’s also a priority to keep pigs growing efficiently to maintain pig flow, maximize facility use and capitalize on marketing opportunities. But there is less recognition that it all starts with replacement-gilt selection and development.

“Gilts are the foundation of good production, and we have to do it right,” says Jennifer Patterson, research associate, University of Alberta. “We have to recognize that gilt development starts at birth, and that sets up sow lifetime productivity (SLP).”

It’s also important to remember what makes up SLP. “It’s not just the first litter size but also retention; we want breeding females to stay in the herd for a long, productive life,” she adds. “The loss of early-parity sows is one of the
challenges in the industry right now. It’s an opportunity to make progress.”

The exact parity where a gilt starts to pay for itself varies somewhat from farm to farm, but a good goal is for about 70 percent of the females bred to reach parity 3.

Three Selection Stages

There are many factors that play a role in determining whether a gilt makes it to the breeding herd, not the least of which are genetics, health, nutrition, stocking density and building environment. But for the actual selection process, Patterson and her colleagues break it into three stages:

Pre-select 1 — This occurs at birth and weaning and is influenced by such things as litter management, day 1 pig care, access to colostrum, and evaluating piglet body conformation and underline. As for individual birthweights, any gilt weighing less than 2 pounds is not a candidate. “There’s evidence that they have increased pre-weaning mortality, compromised growth, fewer pigs born alive at first farrowing, fewer pigs through parity 3 and increased chances of removal,” Patterson notes.

Pre-select 2 — This occurs after weaning to about 140 days of age when gilts are selected to enter the gilt-development unit (GDU). Body conformation, underline and mobility screening apply here as well, along with minimum weight and growth requirements. “It’s another screening phase to make sure the gilt meets the criteria to enter the final selection phase,” Patterson says.

Final selection — This is the most important stage, and it occurs at about 170 days of age. Selection depends on boar stimulation and the gilt reaching puberty. “We need to see good boar contact and early stimulation so we reach our targets for gilt eligibility and mating, as well as for weight, age and estrus at breeding, setting gilts up for SLP.”

The Boar’s Role

As noted, the boar plays an important role in developing the gilt and screening candidates for the breeding herd. Boar exposure around 170 days of age triggers puberty in responsive gilts and allows time for a heat-no-service (HNS), with breeding during the second heat at a targeted weight of 300 pounds to 350 pounds. Research shows that gilts bred at their second estrus produce 1.2 more pigs after four litters compared to gilts bred at first estrus. While it’s important not to restrict feed intake as the gilts continue to grow and develop, research also shows that overweight gilts (greater than 350 pounds) at breeding have more stillborn pigs at first farrowing, a higher removal rate due to lameness and lower lifetime productivity to parity 3 if they remain in the herd.

The quality of boar exposure is important, and Patterson offers these tips:

• Direct contact with vasectomized (teaser) boars is more efficient than fence-line contact to trigger puberty and allows gilts to solicit the boars. Overall, it reduces age at puberty and increases the percentage of gilts cycling.

• Taking gilts to the boar-exposure area is more effective than taking boars to the gilt pen.

• Daily physical exposure to mature (greater than 10 months old), highlibido boars for at least 10 to 15 minutes per day for every 20 to 30 gilts maximizes the response. “A boar could be used a couple of times a day but definitely mix it up. If you have six or eight pens of gilts, you want multiple boars,” Patterson says.

• Have the right sized boars that aren’t too aggressive. “Sometimes people use the boar that’s easiest to move, but he may not be right for puberty stimulation. Also, you want to avoid injury,” she adds. “Every 6 months or quarterly have a boar-replacement plan so boars never get too big and they maintain a high libido.”

• Keep only mobile boars in the mix. They should have no problem walking or standing.

Also, be sure not to house gilts too close to boars to prevent them from acclimating to the boar’s stimuli.

Invest in GDU Personnel

It’s not exactly a revelation that labor plays a key role in a farm’s success as well as its limitations. But if the GDU is where productivity begins, it’s important to invest in developing those workers and provide the tools they need to succeed.

“There’s so much to do on the farm, and people work so hard — there might be sows to breed, farrowing problems or other things that get priority, and then they go back to the GDU,” Patterson notes. “Prioritize these jobs, give them some status and set up a GDU lead.”

Provide a structured on-boarding process for new hires, including learning opportunities and training modules. Management should mentor GDU personnel, offer regular feedback and then follow up. Provide the right tools, such as a proper heat-checking system with the right boars, and make sure workers have the time to do things correctly.

Set goals. The GDU and breeding herd generate a lot of records, but you need the right reports to monitor reproductive success. “For replacement gilts, critical records such as age at puberty and HNS are rarely collected or analyzed,” Patterson says.

Here are the four “must-have” records: age at puberty, estrus number, weight and age at breeding. These key metrics of gilt development should be captured and recorded weekly.

Additional data that can help troubleshoot reproductive issues include:

• Response of successive gilt cohorts to puberty induction;

• Results of tools used, such as PG600;

• Conception and farrowing rates and litter size (total born, born alive, stillbirths, mummies);

• SLP reports, including retention.

Finally, an area where there’s always room to improve is communication between the GDU and the farrowing room. “There is more opportunity to share information,” Patterson notes. “At breeding we’re preparing females to make it to farrowing and the progeny on to weaning. Then we need to get them rebred successfully and make it to parity 2. That information exchange also comes down to records.”

Identifying At-risk Sows

Once gilts have made it through selection, development and breeding, the riskiest stages are ahead — gestation and farrowing. In recent years, sow mortality rates have trended upward. “Since 2014, the annualized mortality rate has increased almost 0.75 percent to 1 percent,” says Chris Rademacher, DVM, clinical professor at Iowa State University (ISU).

Exactly why this has occurred isn’t clear, but the selection of highly productive sows is a likely contributor as sows will sacrifice their own body condition for the litter. There are many reasons why sows die, but the biggest reason is “unknown” or “sudden death” which is a vague, catchall category. Rademacher and his ISU colleague, Justin Brown, DVM, wanted to see whether practical actions on the farm could positively impact sow mortality.

They set up a trial in 2021 with Iowa Select Farms, involving three gestation buildings on a 4,000-head sow farm. The goal was to look at every gestating gilt/sow every day, identify “at-risk” females and expedite the designated treatment from the farm’s standard operating procedures. The animals were housed in stalls and fed once a day in the morning, which provided an excellent viewing opportunity.

Brown oversaw the project, in which every morning for a week ISU veterinarians met with the farm staff for training. An ISU veterinarian and a gestation caregiver made up a two-person team, in which one person walked in front and one in back of the sows to look them over.

“Any sow that didn’t get up to eat was flagged with a card for a more thorough evaluation to determine treatment,” Brown says. “Treatment could be done later in the day when the workers had more time.”

The idea is simple enough, but it’s worth noting that the screeners had about 30 minutes to work through a building before the gilts/sows started to lie down again. So, they had to keep moving.

In week 2, the ISU veterinarians observed the farm staff doing the screening, and after that the caregivers did the job on their own. “In that 2-week period, the staff could already see an improvement,” Rademacher points out, “and they were motivated to continue.”

What They Found

Looking at the clinical signs, being “off feed” was the primary driver for at-risk sows at 60 percent of the cases. The rest broke out as: lameness, 23 percent; respiratory, 7 percent; fever and open wound, each at 4 percent; discharge, 2 percent. It’s also worth noting that 30 percent had two symptoms — off feed and lameness, “which is probably why they were off feed,” Rademacher says. Gilts made up 35 percent of the at-risk animals.

Comparing sow mortality 24 weeks before the intervention with the 24 weeks after, there was a 4.2 percent decline in annualized sow mortality. “The screening was applied only in the breeding/gestation area; we didn’t do anything in farrowing, yet the results applied across all sow mortality,” he adds.

The screening program continued on the original farm, and when Iowa Select determined it was sustainable, the company expanded it to the rest of the breeding/gestation sites. Pete Thomas, DVM, Iowa Select Farms, says all participants, from veterinarians to managers to animal well-being teams and barn staff, received uniform messaging and training. “We made sure we were all on the same page; that’s one thing that’s really helped,” he adds. “We’ve replicated the 4 percent sow-mortality reduction across the system.”

As for the time commitment, the original trial showed it took two people 2 hours a day for the morning screening and one person 1 hour for the follow-up evaluation and treatment.

“There’s a labor component, but if we can keep sows in the herd longer, there’s a pay off,” Brown notes. Using ISU’s economic estimate that a 1 percent change in sow mortality equals $2.80, a 4 percent improvement would add up to $11.20 per sow.

“It comes down to husbandry, checking every sow every day and applying quicker interventions,” Brown says. The ISU veterinarians are hoping to repeat the program on more farms and are creating educational tools for that purpose.

“It’s a simple, practical process that you can do on the farm,” Rademacher says, “and it’s fun to see the results.”

Frank’s Note

There is no shortage of jobs to complete within a hog farm; everyone everywhere is busy. For the breeding herd, typically it’s the farrowing room that gets priority, and certainly assisting sows and their litters can have a direct payoff. Yet, a sow’s lifetime productivity begins with gilt selection at a very young age.

Initiating the replacement-gilt selection process at birth will help the whole gilt development process run smoother. As outlined in the accompanying article, there are three stages of gilt selection, management and development. Each stage offers an opportunity to identify the best candidates to remain in the breeding herd to ensure high productivity, lifetime performance and longevity. Yes, there are breeding targets to meet, and the gilt development process is time consuming, but it’s worth the extra effort to ensure that you’re setting the farm up for success.

Implementing strategies to maximize sow longevity is not only a sound economic decision, it’s also good for caregiver morale and animal well-being. Make gilt development and gestation management priorities by giving employees the training, tools and feedback they need to do the job right. Monitor those animals daily from the start, and take quick action on treatments or interventions to keep them productive for years to come.

You may not think of it as a breeding-herd succession plan, but that’s essentially what replacement-gilt selection and development is, and it’s important to give it the attention it deserves.

Farmweld is here to offer the equipment you need to keep your gilts and sows productive at all stages of development. Give us a call at 1-800-EAT-PORK (328-7675) or visit