Part 2: Optimizing gilt reproduction and development

Editor's note: This is the second in a series of articles. The first article was published in the February issue.

Veterinarians and swine reproductive experts recently shared some of their thoughts about performance criteria they believe is important to assess for gilts in a pork production system in today's industry.

Their comments were made in a roundtable discussion on "Optimizing gilt reproduction and development" held in St. Paul, Minn., prior to last fall's University of Minnesota Allen D. Leman Swine Conference. Intervet sponsored the roundtable.

Indiana swine veterinarian Max Rodibaugh, DVM, moderated the discussion. Other participants included: Joe Connor, DVM, swine veterinarian with Carthage Veterinary Service, Ltd., Carthage, Ill.; George Foxcroft, PhD, swine reproductive physiologist, University of Alberta, Canada; Roy Kirkwood, DVM, PhD, swine reproductive expert, Michigan State University; and Robert Knox, PhD, applied swine reproductive physiologist with the University of Illinois.


Experts say there are specific performance criteria you can use in order to help optimize gilt reproduction and development.

"Within the constraints of any particular management system, it's nice to know the age of puberty," says MichiganStateUniversity"s Kirkwood. "I like early-maturing females because they are likely more fertile than their later-maturing contemporaries."

Ovulation rate
University of Illinois expert Knox says that ovulation rate may be a factor. "Do we miss it at ovulation rate?"

Knox says that the number of eggs ovulated is the first step that can limit litter size. "I think ovulation rate starts the whole process," he says. "I don't think that's all there is to it, but it would be helpful if you had a mechanism for determining the number of eggs ovulated."

He adds that currently there is no test for measuring ovulation rate, but there is the possibility of such a test being developed in the future.

The test could have application for research into identifying problems in ovulation rate. It could also help genetic companies select animals, plus it might be used to help determine specific management strategies to optimize ovulation rate to help troubleshoot low-litter-size problems on commercial farms, according to Knox.

Canadian swine reproductive expert Foxcroft believes that ovulation rate is only a limiting factor to a certain point. "I would argue that ovulation rate beyond parity two is not a limiting factor."

Replacement rate
Foxcroft believes that a key measure of good breeding herd performance is annual replacement rate. "If it's around 65 or 70 percent, you know there's something wrong within the system.


Within the constraints of any particular management system, the age of puberty is something to know when assessing gilts, says MichiganStateUniversity swine reproductive expert Roy Kirkwood.

"Another key indicator of performance would be to look at the number of gilts on inventory compared to the number bred and farrowed," says Foxcroft. "If there isn't a good selection program, it is quite likely that 15 percent of the gilts sent to the sow farms never produce a litter, and indeed they may not even generate a breeding record. They go to the sow gestation barn anyway, then accumulate about 70 non-productive days, they're bred twice, yet never produce a litter."

Illinois swine veterinarian Connor says one pork production system his clinic works with has begun to take a close look at the number of weaned pigs per gilt delivered. "It's shockingly low because of attrition rates and culls," says Connor. "We're going to look at that harder as maybe a measure of driving the system."

Gilt inventory
Foxcroft says one of the difficult questions to answer is "when is a gilt on inventory? It's time we had an honest answer. Some units have very honest numbers, and that's how you can get an honest answer.


The criteria for farrowing rates and litter size should be the same for sows and gilts, some swine reproductive experts believe.

"You say ‘okay, if you have a record of inventory, now tell us how many animals farrow." You'll find that number is traditionally less than 75 percent in units that don't have effective gilt selection programs. Yet you talk to managers who will vehemently argue that they're up around 80 to 90 percent of all gilts producing litters, yet the records don't show it."

Foxcroft believes that this "is an important performance indicator that is very hard to get good information on. First of all, you've got to have a universal system for determining the point at which every animal in the GDU (gilt development unit) is on inventory. We hear that the Dutch put them on the inventory at breeding or that the Danes put them on inventory at farrowing. Therefore, as a first step, we've got to have a system in which gilts go on inventory regardless of what happens later."

Are there more specific individual numbers that you might look at to help you review gilt performance?

Sows, gilts
Kirkwood believes that you don't necessarily need to look at anything different for gilts than what you are looking at for sows, "if what you're talking about is farrowing rate and litter size. If I'm asked to look at a performance monitor and break it down by parity, I'll look at the same things for both gilts and sows."


Illinois swine veterinarian Joe Connor says there is an ongoing debate within the pork industry about what is the best way to measure the economic returns of improving swine reproduction in a system.

Foxcroft says the absolute benchmark is standing heat because that is the only thing you can breed to. "I would want 100 percent recorded heat/no serve. I don't care where it comes from -- whether it's a pharmacological approach or natural induction of estrus. "There are far too many units that don't have records of a standing heat. And that's different from records of vulval distensions and other things.

"However, if you induce that standing heat, you've got to record the standing heat in front of a boar. Then, given the choice, the only thing that would stop us breeding at second estrus would be high growth.

"I don't think there's any debate at all of the economic benefits of the extra 21 days to move to second estrus for breeding. We certainly don't lose money, and you gain a lot of control and time to adjust a number of other things. That's an absolute for us."

Heat no service
Connor agrees. "A high percentage of the producers we work with record heat no service." Connor cites an example of a "period where we relaxed a little bit and allowed breeding tech-nicians to just look at external signs, such as vulvular swellings. That really got those farms out of sync again with respect to correctly identifying  estrus and thus heat no service.


University of Illinois expert Robert Knox, an applied swine reproductive physiologist, says that the number of eggs ovulated is the first step that can limit litter size in gilts.

"I agree 100 percent that it needs to go back to standing heats in front of boars. We probably have 60 percent of herds that do that."

Connor adds that this is an area that needs continual emphasis because of staff burnout. "They'll do heat no service for three to four months and the system is in place, but they're back to breeding on first estrus because they miss breeding targets. It requires continual work to do it right."

Foxcroft says that you need a workable record system in order to consistently do what Connor suggests. "You have to have somebody recording the data and somebody looking at the data and making decisions."

Knox agrees: "I think it's critical to have somebody who has that as their duty, not only to be able to look at heat but possibly even duration of heat. Maybe it's a one-day heat. A one-day heat sometimes brings up false warnings. Most animals will show heat for two days if they're fertile. It's the one-day heats or the one-time heats that, in my experience, are sometimes false heats. Two consecutive-day heats are real."


Canadian swine reproductive expert George Foxcroft believes that a key measure of good breeding herd performance is annual replacement rate.

Knox also would like to see a profile of how the animals are performing in the herds. "For example, looking at what percentage of these replacement gilts are expressing estrus under a particular management system. It would allow you to make shifts in your management system to improve some aspect to improve synchrony, selection, of even culling or gilts.

"It might also give you an indication of the variation, whether you have a bimodal population or simply a normal distribution for estrus. I think that would be useful data, but I haven't been on any units that would be able to provide that."

Next: Some suggestions on gilt selection and how to help clients troubleshoot and remedy gilt reproductive problems.

The economics of improving gilt performance

Can you measure the economic returns of improving gilt performance? Are there target numbers you can use with clients to show them the economic benefits?

Participants in a recent roundtable discussion on optimizing gilt reproduction and development mostly agreed that this is a difficult question to answer.

University of Michigan swine reproductive expert Roy Kirkwood, DVM, PhD, says, "The biggest factor is to get the management correct so you can actually keep this female on the farm for more than one parity. In terms of the cost of the gilt, you essentially have to get out to third parity or beyond before you break even. You have to be able to keep them in the herd."

Swine veterinarian Joe Connor, DVM, Carthage Veterinary Service, Carthage, Ill., says there is an ongoing debate on what is the best way to measure economic returns. "The two things we look at are the number of gilts delivered and how many enter the herd. The cost of the non-entered gilts has to be distributed either over the other gilts or over the pigs. The second factor is what is the lifetime performance of that female?

"Ultimately that drives down the cost of that weaned pig and productivity is higher, or it certainly drives down the genetic cost. It's a large number even though, for us, most of the producers are either on a weaned pig genetic premium or they're buying gilts through a multiplication type system.

"The real opportunity is improving sow longevity and lowering the cost over the whole system or herd rather than just the genetic cost. The big factor there is pigs-produced-per-lifetime female. That is the best way to capture that."

Canadian expert George Foxcroft believes that the total economic impact of good gilt management is the thing we've got the least handle on. "It's very hard to get at those numbers and it takes about a year after you've changed the system to see the total impact.

"It is really tough to get production system (managers) to believe you for a year, particularly if you get a wreck like a horrendous hot summer or a disease outbreak, then it's even tougher to get them to stay with you.

"The sort of stuff that Joe (Connor) and others are doing, allied to whole system benchmarking, is the only thing that integrates the overall value of the improvements in the gilt development programs we're working with."

Foxcroft believes that eventually the North American pork production industry will be forced to come to grips with inefficiencies in the breeding herd.

He used the pork industry in the Netherlands as an example. "If you were in the Netherlands, running the levels of efficiency typical of big breeding herd operations in North America, you couldn't possibly stay in business.

"It's only the current market scenario that allows that. If you had to pay the environmental cost of feed (such as is the case in the Netherlands) that should never go into a breeding unit, that's going to be the difference between staying in business and going out of business. I think this is absolutely the worst part of our industry."



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