Although improving gilt reproduction and development is a current focus in the North American pork production industry, there is still much room for improvement, according to some experts.

Editor’s note: This is the first in a series of articles.

More attention is being focused on optimizing gilt reproduction and development as a target for improved efficiency in the North American pork production industry.

However, while progress is being made in this area, the extent and consistency of this progress seems to be debatable.

This was apparent from comments by participants 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 Services, 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.


Modern pork production systems are driven economically more by factors other than swine reproduction.

Little progress
In answer to the specific question of how gilt reproduction and development has evolved over the past 20 years in the North American pork industry, Foxcroft says: “I think we’ve made very little progress. We have the same information about gilts now, 20 years later. We’ve built systems that have largely ignored the gilt.”

These modern production systems, Foxcroft explains, usually are driven by nutrition, rather than reproduction. This, he explains, “is not surprising because that’s where the money is made, and that’s where the costs are. Largely, the problems we’re dealing with now are no different from 20 years ago. We still haven’t figured out how to get focused on the importance of the gilt.”

Kirkwood believes the biggest factor is that “the modern gilt is later maturing; a leaner gilt, and it’s more prolific.” This, he remarks, “creates difficulty in management.”


Illinois swine veterinarian Joe Connor says pork producers still struggle with gilt delivery schedules, cycling and service targets, among other things.

Knox agrees. “The historical gilt was a much fatter, slower-growing animal.” Knox says that he does not think there has been a whole lot of genetic progress made “on the reproductive side, but management systems for housing, nutrition and reproduction have, and we’ve seen overall reproductive litter traits go up. Selection systems arecertainly better, along with growth characteristics, but on the reproductive trait side we’re still very similar to where we were 20 years ago.”

“I don’t think the performance of reproduction has changed a lot (even though) I think the gilts are actually more fertile now than they were,” Foxcroft says.


Indiana swine veterinarian Max Rodibaugh, who moderated a recent roundtable discussion, says that the best plans don’t always work out when trying to manage gilts.

In denial
Further, he remarks, “I think we’re in denial about what’s possible, and we hide behind bad production systems believing a lot of false statements.”

He points to research that shows it is possible to have 12 or more live-born pigs in first-bred gilts and a nearly 100 percent farrowing rate. “But then we hear statements, such as ‘a 75 percent farrowing rate is sort of all right or the norm, and 10-born live is sort of the norm.’ Those aren’t norms. The gilts that are being produced are tremendously fertile. We just haven’t figured out what are achievable numbers. The best people get those numbers.”

Illinois swine veterinarian Connor says, in his experience, there have been improvements in gilt productivity. These improvements, he explains, have been driven by a desire to improve herd productivity and the realization that there are definite genetic-environment interactions.

“What we lack is consistency on individual farms with the information or technology that results in consistently high litter size,” says Connor. “We continue to be challenged by how to manage and flow gilts in consistently. Producers still struggle with a gilt delivery schedule, cycling, service targets and meeting service, age and weight targets.


Canadian swine reproductive expert George Foxcroft believes that performance indicators are frequently not met in the gilt development sections of big commercial pork production units.

“We work hard to make the system work for individual managers, but managers frequently still don’t understand the consistently right way to handle the gilts. We’re all trying to get a system so that they can’t fail. As herds get larger, we’re still doing a lot of things that are not correct to optimize gilt performance on an individual herd.”

The PRRS factor
Connor adds that one of the big factors that has driven improvements in gilt development in recent years has been, in reality, PRRS. “As we have been trying to set up programs to manage PRRS, the gilt development emphasis has been coming four or five years later.”


Michigan StateUniversity swine reproductive expert Roy Kirkwood believes that the modern, later maturing, leaner and more prolific gilts sometimes are difficult to manage.

Foxcroft believes that improvements such as those Connor points out may be more an exception than common in the industry. “Performance indicators are frequently not met in the gilt development sections of big commercial units,” he says. “Yet, they stay in business and may have hundreds of thousands of sows in production. Because the management focus tends to be where production systems make their value-added money (such as processing and packaging), primary production becomes a pretty low priority in many of the systems.

“Joe (Connor) and others who work with very focused production systems where the dollar is made at the primary production level, know what a breeding herd has to do for a living when they’re not integrated. Then you see tremendous breeding herd performance, and you see what the animals can do.

“The people who focus on making money on farrow-to-wean will tend to have the very best performance. Where it’s a totally integrated operation, where it isn’t farrow-to- wean, it’s the finished pig in the system and value added to that pig that makes the money. But there’s much less focus on maximizing production efficiency in these types of systems.”

Lack of consistency
University of Illinois expert Knox says there is a lack of consistency between farms in gilt development programs.


Robert Knox, University of Illinois, says that on the gilt reproductive side, the pork industry hasn’t really made a lot of progress in the past 20 years.

“I don’t think there’s much consistency on the farms that I see,” he says. “I think it stems from the variety of farms that are out there. You have variation in pen sizes, numbers, genetics, and each individual system has a unique way of dealing with that on a management level.

“I think there’s a lot of desire for consistency, but it doesn’t seem to translate into the implementation stage. The consistency that everybody would like to have is being able to select gilts at the correct age, at the correct weight and at the correct maturity. At least that’s the consensus on a gilt when she’s reached an appropriate body weight.”

Knox adds that there’s some uncertainty about what the appropriate body weight is. “I think the desire is to mate an animal that’s cycled two or three times, has correct body structure, etc. The desire for that consistency doesn’t match the actual consistency in the replacement pool across the systems.” Further, Knox explains, “because of the differences in the systems, that also sets up problems in developing a uniform method to achieve that consistency.”

Breeding targets
Kirkwood says that “even if there is some level of consistency in terms of what people want, the bottom line is this mind-set that you’re going to meet your breeding targets regardless. You might think you need to wait another cycle on a batch of gilts, but you need to breed them now. Some people know what they should do, but they don’t do it out of economic necessity.”

Indiana swine veterinarian Rodibaugh says this situation is very common. “We have a herd we’re working with right now where there was a health issue, so we couldn’t move gilts into the sow herd. They are breeding gilts earlier and at the wrong site, and then they’ll move them later.

“Those things happen day in and day out. The best plans do go astray. That certainly contributes to some of the inconsistency in the program, even though we might have what we think is a good model set up. Some of that you’re not going to be able to avoid. You could get into a long discussion about what they really shouldn’t do in those instances, but most production units are going to err on the side of getting the breeding target met.”

Kirkwood adds that there also are inconsistencies within a farm or production system. “The classic is how many gilts you bring in the summer when you expect a five to ten percent drop in farrowing. If the facility is run to capacity, there will be little space for additional gilts. So producers crowd them in the expectation of normal estrous behavior. But crowded gilts likely will not behave normally, and that’s really going to mess things up. We’ve grossly undervalued the gilt.”

Foxcroft agrees that summer infertility is “obviously a big issue. In the good times of the year, we have to fill the herd with absolutely premium animals. That means not to include probably 15 percent, or if you want to get really generous, 20 percent of the more marginal gilts that are available. “I think that gives you the leeway by taking those opportunity animals, putting them in just to meet breeding targets. Other people have pushed out to 90 percent of gilts being introduced, but you’ve only got to look at their high annual replacement rates.”

Connor says that the key economic driver is hitting service targets. “It really comes back to how we keep these females in the herd longer. We surveyed a number of herds a year ago, and these herds receiving weaners were allowing 93 percent of them into the herd, even though we target on average a 70 percent entry rate. A herd is going to cull or have so many deads per week, and the rest has got to be made up by gilts.

“You have to restrict culling because those were static inventory herds, given a set number of gilts, a set program, yet a combination of deads and what they perceive as older-parity culls or reproductive culls are going out of the herd at a very high rate at the trade-off of gilts that are available.

“The difficulty we have is trying to slow that down and still hit breeding targets. It still gets back to what we have to do additionally in developing that young parity animal and retaining her in the herd.”

“A lot of operations end up in that situation,” says Foxcroft. “You almost have to have a moratorium for six months where nobody looks at any numbers because you just have to break the cycle. Once you have a 90 percent demand because of what’s happening to the back end, you’re locked in.”

Next: Gilt performance criteria and some economic considerations for optimizing gilt reproduction and development.