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Gilt selection: Too often overlooked in the sow mortality equation

1 September 2021, at 8:44am

One way to advance sow productivity and longevity is to select the right replacement-gilt candidates and prepare them properly for the job ahead. Sow farms have well-established health protocols in place, but individual gilt-selection criteria are less consistent and the push to meet breeding targets often takes precedent.

If gilts are the future of the sow farm, their selection and preparation to enter the breeding herd deserve more attention, according to panelists at an industry roundtable, “Optimum sow care: Keys to improving well-being and longevity.”

“I get to manage a system that has its own multiplication with enough gilts; I still don’t think we do a great job of selecting replacement gilts or that we totally know what to look for,” said Ross Kiehne, DVM, who oversees sow farms through the Swine Vet Center, St. Peter, Minnesota. He acknowledged the research and guidance that’s developed regarding selection criteria for feet and legs. “But I don’t know if we truly know how those factors lead to longevity. There probably needs to be some better studies on selection criteria.”

He also cited industry expansion in the early 2000s as adding to gilt-selection pressures and insufficient caregiver training as contributing to sow mortality challenges.

“I agree that gilt selection and industry expansion might somehow be tied to increased sow mortality,” said Jason Ross, PhD, Iowa State University and director of the Iowa Pork Industry Center. “Giving every potential gilt the opportunity to become a sow could come back to haunt us. We put a lot of emphasis on breeding targets, but if you ask [a producer] if you want quality gilts or if you want to hit breeding targets, the answer is both — and gilts will get bred.”

Both Ross and Kiehne agreed that more work is needed to improve replacement-gilt selection, in order to create better future sows earlier in life and find key development components that will yield sow longevity.

Premature exit

Industry data shows that the average annual sow mortality rate rose from 4.3% in 1993 to 10% by 2017. As Ron Ketchem, co-owner of Swine Management Systems (SMS), relayed, “We’ve seen sow mortality go up about a half a percent a year.” Tracking more than 1.5 million sows, the SMS database also shows a rising trend in young-sow mortality rates, with death loss in parity 0 (P0) to P2 sows exceeding 40%. Ketchem added that culling rates for those females also run close to 40%.

Brigitte Mason, DVM, Country View Family Farms, has seen a similar trend with P0, P1 and P2 sow deaths and culls in their system. “They’re the ones we’re either culling or euthanizing the most out of our entire farm.” This has prompted a re-evaluation of their gilt-selection program. Among the changes is to take a close look at the animal’s feet and legs. “For instance, we aren’t picking gilts that have cracks all the way up to their coronary band,” she shared.

Given that lameness and injury rank No.2 overall and account for 29% of sow mortalities, according to a 2018 Iowa Pork Industry Center sow study, it’s valid to evaluate the structure and condition of feet and legs not only at selection but also throughout the sow’s life. John Deen, DVM, PhD, swine epidemiologist at the University of Minnesota, relayed that he and his colleagues developed a point system to score gilts based on structure. “The basic driver was the shape of the legs. The gilts with higher scores had better longevity,” he noted. “But while a structural rating is important, it’s often driven by that interaction between [gilt] supply and demand.”

Expanding and evolving systems

Country View’s sow mortality rate doubled in 2019, and that’s “something we have to get under control,” Mason told the group. Notably, the system also went through a rapid expansion in recent years. “We went from a totally crated system to a large-pen, open-gestation system with 285 sows per pen,” she added. “The management piece of that is extraordinarily difficult.”

She acknowledged that perhaps some of these industry changes occurred faster than swine genetics could change. “There were these big changes and maybe the animals weren’t ready or able to manage those changing environmental situations.”

Dyneah Classen, DVM, Carthage Veterinary Service, shared her experience moving some sows into pen gestation, noting that adjusting to pen gestation can easily add to sow mortality rates. But like most things, it’s a multifactorial outcome. “Open-pen gestation typically has a higher sow mortality compared to stall barns,” she said. “However, there are stall barns [under her watch] with 13% mortality and that leads to frustration.”

Roundtable participants agreed that gestation housing deserves a deeper look. Ketchem cited SMS records’ analysis from several years ago: “At that time, there was no difference in death loss between pen and crated gestation. I think that’s different today, but I don’t think we can blame it all on housing. There are lots of things we’ve done differently.”

He added that SMS is working with some of the genetic companies to collect more details about farms’ gestation housing, feeding systems, group-pen sizes and the like, to better understand what’s happening today. He opened the offer up to anyone who was willing to share data with SMS.

Developing gilts right

The panelists agreed that a critical but daunting priority is to identify the key, lead measures within gilt development that will yield results on the sow farm. “Everything we measure is an outcome,” Ross said, “and I think we don’t spend enough time thinking about things that influence [the sow’s] outcome. It’s going to be really hard to make progress unless we start earlier and identify what the influential metrics are.”

One of those lead measures is the gilt’s age at puberty. It’s one of the best indicators that no one tracks, Ross said. “It’s the same for sow longevity and sow lifetime productivity because it’s hard — right? We can measure survivability too, but I think that will be less of a focus if we’re doing things right earlier on.” Of course, these things are all easier said than done.

In an attempt to gain insight into puberty, gilt development and productivity, Ross and his team conducted a study involving vulva scoring. They evaluated gilts at 15 weeks or 105 days of age, measuring the width of their vulva. The data showed gilts that ranked in the bottom 20% for vulva width produced at least one less pig per litter than the 80% that scored average or above average for vulva width. “The percentage that will reach second parity also is different between the two groups,” he pointed out.

They hypothesized that follicular development starts earlier in some gilts than in others. This underscores that some traits may help identify gilt prospects prior to puberty when selection decisions are typically made. Identifying those traits may help classify gilts earlier that have a high probability for success on the sow farm and those with low probability. “And we need enough of them so that we don’t need to select gilts with a low probability for success,” he added.

Building better data

Part of the dilemma of getting a true picture of how gilt development and selection influence sow productivity and longevity is a breakdown in recordkeeping systems. For the most part, until a gilt is bred, she’s not entered into the breeding herd records.

Put simply, “we need better gilt-development data,” Ketchem said. “Say we started with 100 gilts. How many actually saw their first litter? How many saw their second litter?” He noted that data doesn’t exist because farms aren’t recording it and making it a part of their analysis, which makes it difficult to know what’s happening and what to address.

He continued that thought: “If I buy a group of 100 gilts, how many of those should I be able to breed? Is it 50% or 60%? Breeding-stock companies can give us an estimate, but there are no real data enabling us to adjust our selection to meet breeding targets.”

Ketchem’s take-home point is that farms need to collect that data. “Record the animal once she hits the farm or reaches 100 pounds — any way to track that information so we can give better feedback on what’s really going on,” he said. “The information is out there; we just need to be able to collect it and work with it.”

This recordkeeping challenge sparked Mason’s interest, and she relayed a commitment to track data early in Country View’s gilt-multiplication process before gilts enter the breeding herd. “There’s no reason we shouldn’t start doing more tracking ourselves, especially with how we flow our gilts. That’s something we just kind of let go by the wayside, and then we worry once a gilt enters the sow unit,” she said.

But, as she noted, because replacement gilts are on the sow unit beginning at 10 weeks of age, it’s feasible to collect more information and use it to make decisions. “These are some of the points I’m definitely going to be bringing back to my production team,” Mason told the group.