[SOUND] Welcome. In this video, what we want to do is to take a little bit closer look at what's happening around the time of parturition especially during that very early lactation phase. So let me remind you of some things. Again,this bar is parturition. So lots of things are happening around that time frame. This is what I want to review very briefly for you. Mammary gland growth is occurring during pregnancy and then continues after that. In a species like this with a pig, it's actually continuing quite substantially after parturition, after the young are born. We also have colostrum formation. And that's, typically, starts a little bit before parturition in a species like this, and extends maybe just a teeny bit after parturition. Lactogenesis, recall lactogenesis. This is initiation of lactation. We've talked about two phases. So the secretory differentiations, secretory activation. We'll get back to that here in just a moment. To remind you that with that process, the total process of lactogenesis in a species like this, is actually occurring right around, and immediately after, shortly after farrowing or parturition. Compared to say the cow, where the cow's lactogenesis actually starts back here, prepartum a good bit. So they're well into that process by the time they have their calf, typically. And again, fetal development occurring obviously in utero, and after the young are born, neonatal development relying really very much on the continuation of this lactation process. So what I want to do now is to kind of take a closer look at what's happening right after parturition occurs. And we weigh that piglet. This is piglet, weighted over there on the y-axis. The only change we should see should be a result of whatever they're ingesting, whether it's colostrum, or milk, or whatever the case may be, because there's nothing else there for them to eat really at that particular, that real early stage. So, if we look carefully at piglet weight, and we're not talking about weight gain, but weight. What we find is early on, they are increasing in weight. So, there's some weight gain, yes. But then it kind of flattens out a little bit. So, it's like the mammary glands kind of got some fluid there. And most mammals are born fairly maybe scrawny. They're packing a little bit of fluid volume when they've taken their first milk or colostrum, so some of this weight increase is going to be because of that. But then they seem to level out a little bit until that 34 hours, and then all the sudden, starts taking off again. Again, to remember, the only way they're going to be gaining weight, it all in this time frame is going to be from whatever they're getting from the mammary gland to the sow. So it seems like the gland is kind of coasting here, not making a lot of milk. They're not losing weight but they're not making a lot of milk. And all the sudden, it starts to take off and they start gaining weight quite substantially. So let's have our next slide. So we put that in the context of this idea of lactogenesis, initiation of lactation, and the idea that there's a secretory differentiation. That's the first phase where the tissues are kind of getting going and getting all the machinery to make milk, and it's starting to make some secretion. And then the idea that there's kind of the switch-over for secretory activation, where it starts making what we call copious milk secretion where lots and lots of milk is being made very, very rapidly. You can kind of start to see that in this inflection point here. So roughly at about a day and a half, approximately, after giving birth is when we start to see the second phase of lactogenesis occurring in this species. So this is really kind of a nice break point in terms of early lactogenesis here, it actually starts just prior to when the young are born, comes along this period. And then after about roughly a day and a half, copious milk secretion gets started. What we just saw a moment ago was the change in the piglet. Now, let's take a look at the change in the mammary gland during this very early, few days of lactation. So what I've got here is the zero lactation is the time of farrowing, and then day five of lactation. And what I've done is just to give you a relative idea of the mass or the size, in this case, the DNA content, which means the number of cells in that mammary parenchymal tissue for the different glands. So if you recall the 3, 4, and 5 on average are the largest glands. The 1 and 2 are the next largest. And then 6 and 7 are the quote smallest of the glands. So we can kind of see that sort out here, although obviously, there's a little bit more variation. So four and five are the biggest. 3 and 2 would be the next set here, I've colored those in yellow to distinguish them. 1 and 6, and I put 7 down here, and again, that's relatively small compared to tall the rest of them. So that's kind of the distribution of the DNA content, or we can think of it in terms of the total mass of the mammary. Those mammary glands, again, 1 through 7, at the time of farrowing. Now, if we take a look at what happens then between this time point and those same glands, in this case, we're going to start with 1, 6, and 7, at day 5. Let's go to the next slide. What you find is that these actually grow in those 5 days. So they're increasing in mass, they're growing. Go to the next slide. If we look at the 2 and 3 glands, which are kind of intermediate here in terms of size, well, they grow a little bit, but they don't change a huge amount. But then if we look at 1, or 4, and 5, the biggest ones to start with, they actually regressed. So, what is this telling us? This is telling us that, and the other key thing I need to point out here is, with the exception of number 7 here, I'll get back to that in a second. The birth weight was pretty much standardized for 1, 2, 3, 4, 5, 6 glands. So about just slightly under 1.4 kilograms for those birth weight of the piglets that were suckling those glands. So the milking machine essentially was constant. The piglets were a constant weight to start with. The glands, on the other hand, were different. And so there's a different response. These glands were small, the piglets were demanding more milk from that. And so those glands were actually stimulated to grow. These glands were just about right. They didn't change a whole lot up until this point. Well, these glands actually regressed because they were in, essence, too big. They were making too much secretion, there wasn't that much secretion needed. And so they actually regressed until they got to this point here at day 5, to accommodate the size of the piglet. The exception being the piglets that were here were actually more like 1.1 kilogram. But even then, they stimulated that gland to grow, number 7 gland. So up until that point, you can see the distribution here is really shrunk down. So they're much more similar in size. Certainly, still different in size but by day 5, they somewhat similar in size. Go to the next slide. And the key is then after this point, they all grow. All the piglets grow, all the mammary glands grow. And everything's moving up in terms of the mass of the mammary gland. In our previous graphic, those glands were suckled, and so that was causing them to change and then grow later on. But what happens to the glands that are not suckled? So this is an experiment done where we, the question was asked. What happens when the glands are not suckled during early lactation? In this particular case, what they did was they took the cells prior to when they had their young. They would tape off certain glands, and that's what this yellow rectangle represents. So that when the piglets were born, they didn't have access to that gland. And then at certain times after giving birth, they would pull that off, put a piglet on that, and then look at what was the response of the mammary gland. This was very simplistic way of thinking about or looking at that. And so if the gland was what they call closed, that means it was taped off until farrowing or basically wasn't essentially taped off at all. The piglets have direct access to it. Then piglet weight gain was what I'm calling 100%. So I'm putting everything compared to this because that's our kind of gold standard in terms of having access to that gland as soon as the piglets are born. On the other hand, if the gland was taped off for 24 hours or it was not suckled for 24 hours, take the tape off, put a piglet on it. Then they've lost about 15% to 20% of their weight gain compared to the ones that had access right away. So it's already dropped a bit. If we wait until three days, 72 hours, to take that tape off, put a piglet on it, the piglet will not thrive. It will basically not survive. There's just no weight gain at all. What's that's telling us is that within that 72 hours and probably even before 72 hours, that gland has shut down, and it's not going to make any more milk. So there's really no access to milk. So that gives you an idea of how fast that gland is regressing. And particularly how fast it's functionally regressing. How fast is it stopping the process of making milk? So again, this idea of very, very early lactation is incredibly important for the piglet, for the development of the mammary gland, as well as in what's going to happen later on in that lactation. Let's quickly review what we've talked about in this video. We've talked a little bit about lactogenesis. In the pig, this Lactogenesis process is occurring right around the time of parturition and then very shortly thereafter. And we've seen that in terms of some of the things we've looked at. Again, this idea of two stages of lactogenesis, secretory differentiation and secretory activation. Secretory differentiations at first though, day and a half. So again, the first roughly day and a half after parturition, the glands kind of getting itself together. It's making a little bit of milk but not a huge amount of milk at that point. And then we shift to seeing the shift into this copious milk secretion after that point where making a lot of milk, the pickles are starting to grow much more rapidly. So again, we can really see those stages fairly well in the pig as we look at piglet development in a very early part of after birth. Mammary glands adapt to suckling demand which kind of gets back to here. Again, the mass of the mammary gland might be bigger, smaller than meeting the demands of the piglet. If it's too big, the piglet doesn't need all of that milk that is being produced. It's being produced then the gland will regress a bit until they can kind of equilibrate. The reverse is true with the piglets bigger than what the mammary gland can provide. It's going to cause that gland to stimulate that gland to grow until they kind of come at equilibrium. And then after, again, several days, everything's starting to grow. Both the mammary gland and the piglet are growing after that point. And then finally, the idea that if milk is not removed from the gland, very, very early on, then we get a rapid loss in the functionality of the mammary gland. We saw that within three days, it's basically not making any milk at all. And again, we probably could back that up into two, two and a half days, something like that, where it's probably not making very much milk, certainly not enough milk to maintain that piglet that's nursing that tit.
