[MUSIC] Welcome back, in many of the videos that we've done in this course up till now we have focused on the dairy cow as our primary model. For understanding concepts of lactation, of understanding how lactation works essentially, of how it manifests itself in that particular species. We've also used another species from time to time, that is the pig or swine or lactating sow as an example. And in this set of videos, I want to expand on that, I want to pull that information together from the lactating sow and one spot and talk about the cell in particular. I'll still go back and use cows and sometimes humans is a counter point to our contrast as we think about how things happen in the cells. So, let's start off with the first slide here just to remind you of the lactation cycle in the cow, start off with kind of where we've been and again, lactose cycle in the cow. She has a calf, she lactates for about ten months, usually, it depends upon the circumstances but about ten months, that's the white bar coming around here. We dry her off, we stop milking her and then about two months later she has a calf and so ideally, we like to have her doing this in an annual or yearly cycle. Go to the next slide, and I put on here in the pink is when she's pregnant, so in this particular species many times they are able to conceive here, early in lactation and they are lactating and pregnant at the same time. And then again, we draw her for about two months prior to having her next calf. She's pregnant the last part of the pregnancy has her net calf and starts another lactation, so that's a cow, so in this particular species they can be or the way we manage them, they are pregnant and lactating at the same time. Go to the next slide, this is the sow, the pig and so she has her litter, she lactates for about and typically we would wean the piglets at about three months, excuse me three weeks, 21 days is approximately a peak lactation, so we wean them about that point, about seven days later they will come into estrus, they're bred. And then they're non-lactating, that's the yellow bar and then pregnant, the pink bar coming around till they have their next litter, so this is a species in which the way we manage them at any rate, they're typically not pregnant and lactating simultaneously. Another feature that's different between the dairy cow and the sow is it gets back to this idea of milk removal, so it reminds you in the case of a dairy cow, we have this thing called the milking machine, it's made of rubber and steel, it's pretty much constant. You put the machine on there, we decide when they're milked, except in a situation like a robotic milker where a cow might come in three to five times a day. We decide usually people are milking cows, in this manner, two or three times a day, and we decide when that happens, so we have a lot of control over the milk removal process in terms of the way we manage dairy cows, again this is steel and rubber, they never changes and typically. Next slide, on the other in sow this is the milking machine right here, this will guide, and there is a whole bunch of them and they are constantly changing, they are constantly changing in terms of the growth and metabolism. And so on and so forth, the demand of the mammary gland is changing over time so it's a much more fluid situation than the case of the cow, so here we control a lot of the lactation in terms of how she's producing the milk, here the piglets are in the litter are controlling a lot of what's happening in terms of lactation, we need to keep that in the back of our minds. As we think about what the sow was doing in terms of lactation, so some other factors that come into play in terms of difference between cow and the lactating sow, and these are several other things that are really important for us to keep in mind as we think about milk production, lactation in a sow. One of those is there is a very tight teat order that is established in by the litter, by the new born pigs. Let's go with the next slide, and this, just to give you an idea of what I mean by teat order, this piglet only nurses that gland, this piglet over there only nurses that gland, in other words, they don't move around, so this piglet doesn't suddenly start nursing that gland up there or this gland back here. This is the truth of the kinds of breeds of pigs, swine that we have in North America and Europe. There are some other breeds for example some Chinese breed of pigs where apparently this is not true, where they basically will nurse whatever's available. But in terms of the kinds of information, I'm going to be sharing with you, we're talking about pigs, swine, that are of this nature, they have a fairly tight teat order, it's not absolute. Some on occasion you'll have one piglet trying to keep two glands going at one time, but typically they only nurse one gland and it's only the same gland each time, and again, we'll come back to that here later on in terms of the impact of that on the cell lactation. Let's go to the next slide, in addition to teat order, synchronized nursings occurring, that is all the piglets are up at the same time and this gets back to milk ejection and maternal behavior and those kinds of things, as well as some other kinds of maternal litter behavior interactions. So again, remember in the case of the dairy cow the milking machine, the machines all, we control that, it's the same all the time, whereas, here again, relationships between mother and litter are changing. Again, the litters getting bigger, they're demanding more from the mother, some moms some of the sows are really not very good in terms of how they lay down, and move and turn over and allow the piglet access to the mammary glands. Whole range of kinds of things come into play, this is more of a generic way of thinking about the behavior or relationship between the litter and the cell. One of the reasons I put this up here is to remind myself to tell you that this teat order and synchronized nursings, and a lot of are already established within the first half day after they give birth. So within the first 12 hours, actually, even slightly less than that Teat order is really already established, synchronized nursings are established, so it's really only that very, very early part of the period where there's a lot of flux and changing in terms of litter and which piglets are nursing which teats and those kinds of things. By the first half after birth, that's pretty well established after that point. Let's go to the next slide, so another feature is this idea of teat preference. So this is situations where a litter size of perhaps ten, you can see, if you count down here, she's actually got seven glands on each side, the circles, that's what that represents, so she has 14 glands, so if she had 14 piglets, all those teats would be nursed. In this case if we look it, she only has ten piglets on her, then typically the anterior glands are more likely to be nursed. So again, gland location over here, 1 through 7, and then 80% of the glands are suckled of number 1, and down here to only 38% of the rear glands are suckled. So again, there's a preference for them to suckle the glands, again, 1,2,3,4,5 down to maybe 6, something like that, and then those last glands, there's less of a preference, it doesn't mean that those glands are not suckled at all, it just means there's less of a, much less likely when you have a little bit smaller liver size. We also will find out in other videos that these glands up here typically are the ones that develop the most and therefore are producing the most milk. One of the things I need to make sure you understand is the following, again in the dairy cow, we know a lot of information about lactation in and how the mammary gland develops in the heifer and during first pregnancy and so on and so on, and then also in multiple lactations, not so much true in swine. We know a lot about or a fair amount about what happens in the gilt that is the first pregnancy, the first farrowing, the first lactation. Again, we know a lot of this because research had been done on those much less, proportionately, about what happens in subsequent lactations in this species. So again, we know a lot from the gilt, and we have to kind of keep that in mind as we go through, and you'll see that you see some of the kinds of things I'll present. Now we're really talking about that first pregnancy, that first lactation, that's where we're getting a lot of our data at this point, we know relatively less about subsequent lactations. Now let's review very quickly what we've talked about in this video, again comparing dairy cow and sow The dairy cow obviously lactates for a much longer period of time than the sow does. So ten months versus basically three weeks, in the case of the sow, the cow typically is pregnant during much of her lactation, the sow is typically not pregnant and lactating at the same time, we've also looked at the milk removal, in other words, the milking machine on the cow, it's very regimented, it's very standardized. In the case of the sow on the other hand, the piglets, different numbers of piglets, they're growing, they're constantly changing, they're constantly changing their demands on the mammary gland, demands on the sow in terms of milk production. So again, that part of the equation is constantly shifting in the case of a species like the sow. When you stop and think about it most of the species, other than dairy animals where we are managing their lactation, so the sow in that sense is more like most other species, humans and other species as well. We've also talked about the fact that in the kinds of breeds of pigs that we have in North America and Europe, there's a very tight teat order, so this piglet only nurses this gland, it doesn't move around and nurse other glands. Synchronized nursings, where all those piglets are up at the same time and that feeds back into some very key behavioral relationships during the milk ejection process and we'll explore those in some other videos as we go along, and they have teat preference. This idea that typically the glands up here are more likely to be nursed in a smaller litter, versus the glands down the inguinal region, so we've covered, talked about a number of those kinds of things, and we'll explore those later on in other videos.
