Back to the basics in gilt development with Dr. Kara Stewart @ The Swine it Podcast Show

“I think for a while the gilt development was kind of a forgotten piece of the sow system and I think it is our greatest potential for improvements in sow reproduction and lifetime performance. We need to start paying more attention there.” – Dr. Kara Stewart

I had the chance to chat with Dr. Kara Stewart about gilt development. If you are on the go, you can hear the episode at Apple Podcast, Spotify, or subscribe to our Youtube Channel. Otherwise, read on:

Thoughts on boar exposure

I think this is where you have to go back to the basics. The data shows a lot of differences between full contact and fence line boar exposure. When we're talking about stimulating a gilt to come into puberty, that's very different than trying to stimulate a sow, a post-weaning to express heat.

For boar exposure in puberty attainment, we want to find full contact board exposure. We want the gilts to be exposed to a boar for about 15 minutes per day. That's a long amount of time, actually for every individual gilt in a pen at the GDU to receive full exposure to the boar. The folks up in Canada have done a lot of work looking at bringing the boar to the gilts vs. The gilts to the boar and found that it advanced puberty or easier to detect pigs in estrus if we move the gilts to the boar. That's called the BEAR method. However, that can be hard from a management perspective to have the space and all of that to do that depending on the GDU and the facilities. The other aspect to consider in boar exposure is that continual exposure could be bad. Gilts kind of become habitual to a boar if he's housed in an adjacent pen, so then they can delay puberty as well. Thus, we want individual gilts, full contact, 15 minutes a day is best.

Thoughts on optimal weight, age, and number of estruses

The two groups that I know of that I look for a lot of research coming out in gilt is Dr. George Foxcroft and Jennifer Patterson up in Canada and then Clay Lents and his crew out at the US Marc. Both groups do a lot of work with gilts. But I still think the target breeding weight we could argue is around 300 pounds (135 kg). Breeding age should be no longer than 220-225 days of age. If you aren't getting those gilts bred by 225 days of age, they are not going to maximize any reproductive potential for your farm. I haven't seen anybody repeat some of the data, but breeding at the second estrus, the data was pretty clear that it increases ovulation rate and number born alive. Thus, it's worthwhile to skip a heat (only document that heat) and breed at the second estrus or third estrus. I don't think I know of any data that shows a benefit of second vs. Third heat, but anything more than one estrus.

And that's tough... Some GDUs aren't doing a very good job at recording heat-no-service in the barns and the GDU and others are doing a great job of that and confirming they've had a heat before they move them into crates and start getting them ready for breeding.

Thoughts on acclimation to the breeding crate.

I think that's getting a lot more practiced, which I think is great. Those gilts, if they are cycling in the group pens and then you move them into a stall, they do need some time to adjust to that stall and not being stressed. Thus, I think it's really important that we do spend some time acclimating them to that stall and then before they move to the sow farm and get put in a stall to be bred for the first time. And that also makes sure they know how to eat in the stall, they know how to drink out of the right nipple waterers or the trough. They need a lot of those kinds of adjustments, otherwise, we can see them maybe have that first heat documented in the pen and then, all of a sudden, they don't seem to cycle again and they fall out. Part of that just could be acclimation to the stalls.

Once you find them in heat, that first time, if you have stalls at the GDU to put them in to start acclimating them there and by the time they're ready for their next cycle, they should be acclimated. Two to three weeks in their crate would be nice to get them acclimated.

Thoughts on out-of-feed events

Another topic that, in my opinion, it's impactful is out-of-feed events. In two ways: One is that when we look at the growth rate of the gilts if we want them to achieve puberty on time they need to be maintaining a good and steady growth rate throughout all of their development. The data that again, is more than a decade old that said something like 0.55 kg per day. Well, we would easily hit that target in modern-day genetics. We're probably at 0.70 kg a day today. But that being said, I think if they have a lot of changes in their growth rate, it also comes as a big stress for them. No matter how long the out-of-feed event is, that's changing their growth trajectory. And I think it'll impact puberty. And we've had a couple of research trials on commercial GDUs where we had some documented out-of-feed events and we ultrasounded ovaries on those gilts when they should be pubertal and we found that barns that had out of feed events were completely delayed in puberty. My experience with it has been: it's pretty impactful and I think it changes their growth trajectory as well as probably is a huge stress to them. Which all of that will delay puberty.

Thoughts on space requirements for the gilts

Here again, you go back to some of the older data, but I think they looked at 12 square feet per gilt during development and maybe it's more important for us to think about the number of gilts per pen as well as the actual space requirement for the gilt. They looked at group sizes between 10 and 30 seemed to be pretty ideal, but over 30 could have delayed puberty, but that could be the effects of space requirement or number of pigs per pen. I haven't seen a lot of recent data but I can tell you I've been on some GDUs that have some pretty crowded pens and a lot of times they even have maybe a vasectomized boar living in there with the gilts - full time. It's just quite remarkable to me when we think about our industry, how much variation there is in management at the GDUs. I think the more space the better and no more than 30 gilts per pen is still probably where we need to be.

I think a lot of people converted barns so the facilities are very different from farm to or you know, system to system on what the GDUs look like and what they're capable of doing and when they move pigs around. And for sure the methods of boar exposure there is just a lot of variation on what people are doing.

Have gilt development units and gilt research been forgotten?

I think for a while gilt development was kind of a forgotten piece of the sow system. And I think it is our greatest potential for improvements in sow reproduction and lifetime performance. We need to start paying more attention there. Jennifer Patterson and George Foxcroft just put out a review within this past year that discussed managing gilts for their lifetime reproductive performance that I think summarizes a lot of the data over the past 20 years. I think we have recently had this issue where, you know, one, a couple of large systems had gilts not expressing the standing heat reflex and they did some slaughter checks and saw that some of them were cycling. They just weren't ever expressing heat. It wasn't just a small number; it was kind of this relatively large number of animals that all of a sudden just wasn't expressing a standing heat response.

Some of them would have vulvas that swelled up, but then they never locked up and showed the behavior. I think that got a lot of the academics, the veterinarians, and the genetics companies together to start trying to figure out what changed. The good news for me is that put a lot of professionals into GDUs to start looking at management and re-evaluating kind of the gilt portion of our sow performance. I think in my personal experience, that was the first time that has put me on a lot more GDUs in the past couple of years just trying to work through some of these issues that we were seeing with these gilts not standing in heat. Some good research is starting to come out of that and I think that that's going to get us geared up to start maybe putting some more research dollars into focusing on it. We have a lot of potential there to make good improvements in sow productivity by focusing back on the development of the gilt.

The development of the gilt begins at birth, maybe even in utero. If you look at the season of birth, it has been shown that stress during gestation can alter ovarian characteristics. You can go back to in-utero development and that's when gilt development starts, not just in the finishing phase at the GDU. I still think we've got a lot to learn and a lot more to do around consistency or research on methods for optimizing puberty attainment in those gilts.

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