We're back here with Doctor Farmer from Agriculture and Agrifood, Canada. And, again, welcome Doctor Farmer. >> It's a pleasure to be here. >> And welcome to Illinois. And this time, again we're going to continue the conversation of milk production and swine and memory development and swine. We want to take a little different spin on this so let's go ahead and go to the first slide here. And I need to remind you of several things before we kind of get into the experiment we're going to talk about here. And that is animal's, so this is a gland wet weight, so it gives you an idea of the rough mass of the gland. And during lactation, day of lactation here on the x-axis and what we have is suckle glands, recall that there are systemic factors and there are local factors in the gland. So all the glands get the same blood essentially, so they all have the same systemic stimulations. For example, prolactin concentrations in the blood, those kinds of things, but locally again this feedback loop to lactation and other components will determine what's happening on say this gland versus this gland. Again, what's happening there and that has a lot to do whether milk was removed from the gland or not. So once lactation's established, you have to have this repeated milk removal to keep the gland going. So those glands are suckled, or milk is removed, grow. Those glands that are not suckled regress. And this regression pattern is not unlike what you find when you wean the animal out here. So if you go to the next slide. So one of the concepts is that if we say we wean the animals here, this mammary gland undergoes regression. The ones that were not suckled have regressed earlier on but this one doesn't go all the way down. It doesn't regress to exactly the same level. So when they start growing again, which is what these arrows, the implication might be that this gland that was suckled is starting from a higher plane of development versus the one that was not suckled. So this gets into this question of what I call lactational history. What happens in the next lactation? And that's one of the things that Dr. Farmer's done, she's done an experiment to demonstrate this and we're going to talk about that experiment now. This idea of lactational history really, again, gets back to the idea, especially in an animal like a sow, where you have a number of functional teats when they farrow, when they have their young. But not all those teats are nursed and therefore, some undergo involution right away and some are lactate. So we have a couple of examples here of a gland that was suckled, another gland that was suckled over here but clearly this one was not suckled. So again, what Dr. Farmer's asked the question, well does this functionality of the glad during this first parturition have an impact on what that gland does in the next lactation? So let's go to the next slide and she can explain her experimental design here. >> Okay, so what we've done here, actually it was kind of difficult to find the perfect design for this study. So what I've done is, in the first lactation, we had sows that had either 12 or 14 teats. And when I talk about teats, I talk about each individual- >> Gland? >> Mammary gland. Okay, so when they had 14 the two posterior end for the sow were tapped always. >> So the X means that they are taped off? >> Exactly, exactly and then obviously this is the head of the [LAUGH] body of top and the rear of the sow. So basically we have 12 memory glands or teats that were left. And we take six of these teats. In order to take into account the side of the teat and the front and back location, so what I've done is I taped two teats on the one side. >> Up here? >> And then two in the middle, and then two in other side, exactly. And then half of the animal has had this side reversed. So we're taking care of any of, confounding effects that could happen. Now, we had six teats available, so we put six piglets on those teats, obviously. We did not want the piglet to be any important factor in the study. So they all had similar average weight. Then we came to the second lactation, that's where it gets really interesting. The control animals had the same teats that were blocked. So in this case the piglet that's sucking a teat has to suckle the teat that was previously used. >> Yes. >> So that's control animal. >> Previously undergone growth during lactation. >> Exactly. >> Whereas the ones that were taped off had undergone involution or regression. >> Yep, they did not develop at all during lactation. And then when you move to the treated animals, what we've done is that the teat that was taped, was the one that had been used in the first lactation. So, it means in second lactation, the piglets that were suckling were actually suckling teats that had never been used before. And, then what we've done, is we've compared the growth rate of piglets suckling teats that had been used before, control animals, to piglets suckling teats that had not been used before. And then we looked at the difference in growth rate of these pigs. >> So your results were, and I'm going to let you explain your results, but just to kind of let you understand what was said here. So this particular one, we're looking at the mass of the mammary gland, each gland or each teat on day 17 of lactation. And what I've done here is to put the bar and how much mammary growth there is and those that were suckled, those lactations. Then these were not, let me explain this down here. So the 1st Parity here, these were suckled. The 1st Parity is the glands, individual glands and 2nd Parity, so first lactation and second lactation. The yellow bar on the other hand were those that were not suckled the first one or taped off on the first lactation, but were suckled in the second lactation. So have you got a result there? >> Well, this is fascinating. >> Yes. >> Because what we've seen is when you look at the mammary mass actually was parenchymal tissue, so that's the tissue where you do have synthesis of milk. So this parenchymal tissue in the mammary glad was 25% greater when you had a teat that had been used before. So what it tells us is if a piglet, or if the teat is not used in first lactation and in second lactation it's being used, then it's development will be significantly- >> Retarded. >> Less, yes. So, it's important for the teat to be using first lactation for it to have an optimal [INAUDIBLE] in the second lactation. >> So, let's go to the next slide which you'll view the piglets. So, it's a same idea, so for this case we're looking at individual piglet weight gain during this period of time. >> In fact, the significance level was found when we looked at the day 56 weight of the piglets where we saw 1.12 kilogram difference in weight. So piglets that were suckling teats that had not been suckled before weighed 1.12 kilograms less on day 56. And we started with piglets that had similar weight on day two of lactation. One thing important I would like to mention here is that when we looked at the weight gain of the piglets, in the period from day two to day four of lactation, already there was a significant difference between the two treatments. So we did not measure colostrum yield but it suggests to us that colostrum yield might also be effected by this non-use of a teat in first lactation. This is most important for piglet immunity and survival. >> So, what are the overall implications of this for lactating gilts? >> Well, one question I often get asked is, by producers who have sows or in this case gits gilts that are thin. And we know that an animal that is too thin, during lactation when you give a lot of milk, it will lose again more weight and more back fat. And it may lead to what we call the thin cell syndrome, and where reproduction will be hindered, and then also longevity will be decreased. So they wonder can I not overload my primly pairs gilts, so when she farrows instead of putting lets say putting 14 piglets on 14 teats. I put only 11 piglets or 10 piglets on 14 tits to make sure she does not lose too much weight, so she maintains a good enough body condition to remain in the herd. So now I can tell the producer it's okay I have an answer for you. If you do this, all it means is that in the second lactation the teat that would not have been suckled will produce less milk. So it's to the producer, the final decision is in the producer's hand but at least they know they the information to make the decision. >> So, back to my applied perspective again from a basic mammary biology perspective, I find it very fascinating, this idea of lactational history. What happens in this lactation may be predicated on what happened in that gland in the previous lactation. This is going from literally first lactation gilts, to second lactation. We don't really know a lot about what happened to the third, fourth and fifth and so we really don't know what's going on after that. >> Actually we don't know at all. So it would be only speculation. But we presumed and I am quite confident that the major effect would be between the first and the second lactation. But whether there is a significant effect later on if a teat is not used in third lactation I'd say does it effect the fourth lactation milk yield? That's not known at the present time. >> We don't know that. >> Nope. >> We would assume that that would perhaps not be as a big an impact but still there may be an effect. >> Exactly, I'm confident it would never be as big an impact. But is there an impact? We don't know. One thing I forgot to mention. Another project I've done recently was trying to find how long the piglet has to suckle a teat in first lactation for it not to have a negative effect on its milk yield in the second lactation? >> Yeah. >> And I just finished a study where we had sows that had either 2 day lactation, a 7 day lactation, or a 17 day lactation. And in all these cases in the second lactation weight gain of the piglet was similar. So what it tells- >> So even the two day? >> Yeah. >> Even the two day, so even getting colostrum, yeah. >> So what it tells us is that for a producer, if you leave piglets in the first parity, two days on the gland, that should be good enough for it to produce milk adequately in the second lactation. >> Interesting that's again very fascinating yeah. So again it's this idea that very, very early in lactation what's happening to that gland the very first few days is setting up what happens later on in that lactation. But also then carrying over It's only to the next life that takes it. >> Exactly. >> Many questions that we don't have really good answers are and we're starting to get a few answers here. So Dr. Farmer thank you again, it has been very interesting. >> It was a pleasure to discuss this with you.
