Welcome, in this video, we're going to spend a little bit of time briefly reviewing mammary anatomy and a little bit about mammary development in the sow. And again in terms of the guilt, so let's go to our first slide. I remind you that some of the characteristics of mammary glands on this species. The top picture is an animal very close to farrowing, the bottom one, she's actually lactating. You see all the glands here are well developed, they're all full of milk or actually getting full of colostrum. She's just about ready to have her litter. Again, a series of these going from this area down to inguinal region. Typically six or seven on a side. One of the characteristics that you might give some thought to at some point is if you go into a farrowing barn, typically you'll find animals sows giving birth that have again 7, at least 7 on a side, so 14 glands. The reason that that is the case, it doesn't mean that all pigs are like that, all sows are like that. But they're selected in order to go into the breeding herd. They're actually selected to have that many, because of the litter sizes that we have today. So it's important that they have 12 or 14, preferably 14 functional mammary glands. You'll notice a little bit of difference here between those that are close to farrowing, that haven't quite given birth yet, to that which is lactating. And that is we have some glands here that are not functional. So there's a gland right there that's not being suckled. So the front one's being suckled, this one's being suckled, this one's being suckled and there's one behind the bar here being suckled. But this gland is not being suckled, and so it's actually regressed and we'll address that in another video later on. Let's go to the next slide. So to remind you, well again this is just to point out this set of three glands here. This one's being suckled, and so the gland itself is kind of like that. This gland is kind of like that, two glands being suckled and this gland is not being suckled. So it's not producing milk, it's actually involuted. When this gilt or sow had her young that gland was functional, it was producing colostrum. Because it was not suckled though, milk removal is not happening. It involuted in spite of the fact that these others are continuing to lactate and again, milk being removed. Let's go to the next slide. So what I've done here is just to remind you again, that in this species there are actually two glands inside of here. So again, I kind of drawn an outline around each of these in terms of indicating where the gland is. And then draw a dotted line in the middle here to indicate that there is a glad here. And there's another gland right here, and then each of those the milk produced in those comes out of separate lactiferous sinus, separate exit from the teat. And so milk that's produced in this gland does not come out that side of the teat. Likewise, milk that's produced in this gland doesn't come out that gland over there. So again, it's a system of ducts that come down here. And then on this one it would come out here. We can see this a little bit better, if we go to the next slide. Now if we look at the end of the teat, like this on a pig, sometimes it's kind of hard to see those two exits. To really see it very well, we'll actually again sacrifice the animal, pull that teat up a little bit. And then cut off the end of the teat, and that's what we've done here. So this is kind of the stub of the teat, and you can see very carefully here one exit and one exit there which go up into the gland. And so this one, this exit's going to go off into that part of the gland. This exit's going to go off into the other part of the gland. Down here, I've kind of taken the route here and put it inside what we would call lactiferous sinus. So that's one of the two, that'll be coming out that nipple. This image though shows something else. What I've done here, is the glands been taken off the animal. Again the animal is sacrified, the mammary gland is taken off. And one of the lactiferous sinuses here actually, injected, took a thread and a needle up in there and injected some blue dye. And so you can see this is more blue here. And then this side of the gland where the dye was not injected is not blue. So very clearly, this is a different milk synthesizing part of the gland versus that even though, they're right next to each other. They're actually part of the more what we call complex glands. So again remember that terminology, simple gland and the whole thing would be called a complex gland. I've also indicated with the red here, you can just see a little bit of a lactiferous sinus coming from up here, which would be kind of comparable to the one that's over there. Now let's take a look, another look inside the gland and we'll go back to a pre-pubertal animal with very little mammary development. Again this is, what was done here was the tissue was taken out, very thin sections through the tissue. This is basically, the nipple would have been up here. This is basically the base of the nipple. You can see nicely these two lactiferous sinuses coming down. So again, this one once it develops, and you actually develop tissue here, that milk would go out that one, the milk that's produced over here would go out this one. Post-pubertal, remember when those hormones, especially estrogen, progesterone start getting elevated. We start getting some of the more purplish material here are some of the lobules. Again as they develop, and you can't see the lactiferous sinuses quite as well in this particular case. So if we go to the next slide what I've done is to take the post-pubertal, this is essentially the same kind of tissue. So this is what it'd actually look like if you cut the mammary gland in half, mostly fat pad, all this over here is fat pad and this is fat pad. And right in the middle here you see it's a slightly different color and that would be essentially this down here. And so next slide, what I've done is to basically take this, shrink it down. So you can kind of get an idea of just how small that is at this particular point. So again this is just post-puberty, the animals cycling, but really very, very little mammary development at this point. So again, that's the extent of the mammary parenchymal tissue, the rest of this all out here is the fat pad. Go the next slide. So during pregnancy, then of course mammary development's occurring at an increasing rate, so exponentially. Again remember, this is in gilt. So they've not gone through a previous pregnancy, not gone through a previous lactation prior to this. So she conceives, mammary development's increasing, but very, very slow. And as she gets to that last trimester, the last several days, this thing's going up faster and faster and faster. And then when she has her young, and this is actually only day 105. So she still has like about nine days left, but you can see the way these are growing and projecting up. So the data we have in this particular study came up to day 105. Again they farrow at about roughly day 114, 115. The middle glands, middle glands meaning the three, four, and five glands are far and away the biggest. Anterior glands, number one and two glands from the anterior end are the next biggest. And then those posterior glands, the six and seven are the smallest. So you can see, when she has her young, these middle glands are the biggest. Next biggest would be the anterior glands and the posterior glands to be the smallest. Go the next slide. [COUGH] And then this shows you a little bit more of visually in a different way how fast that gland is growing. So we have day 80 of pregnancy, again these are in gilts, the first time they've gone through pregnancy. Day 100, 110, and then a lactating gland, and these are essentially all to scale relative to each other. So in the day 80, you just kind of see this area right in here, would be the parenchymal tissue. The rest of that's all fat pad, so that's what's growing. And then 20 days later, 20 days later, less than 3 weeks later, it's gone to this extent. This is the muscling underneath there. Again fat pad would be over here, and then 10 days later it goes from this to that. Which is getting pretty close to what it would be during early lactation. So just massive explosive growth going on there again, exponential growth as we go along here in late pregnancy. And then this tissue looks not unlike lactating tissue, it continues to grow during lactation. So it will continue to grow, this is probably early lactation. Let's quickly review now, mammary gland on the pig. Again, they're all the way up and down the line here. There are within each complex gland, there are two glands. So there's one here and then one here. Again each of those milk collecting systems comes out a different hole in the teat, a different nipple. A different lactiferous sinus coming out of each of the teats. Mammary development in the pre-puberal or post-puberal, there's not a lot of development. Most of that development is occurring in that first pregnancy, especially in the last third of that first pregnancy. And especially in the last two or three weeks of pregnancy is where you see a lot of that parenchymal tissue growing extremely rapidly. So by the time she farrows, again all glands are functional, all glands are making colostrum. All glands will potentially lactate and then we'll see later on, it's only because colostrum milk is being removed that, that lactation function is maintained.
