[MUSIC] Welcome, want to continue talking about the concept of milk removal, and how it impacts milk production in the sow. So we saw that the litter size can make a difference in terms of milk removal, and milk suckling intensity. So let's go to our first slide and review. So again, we kind of looked at the litter size. And now we want to start looking at some elements that play into the piglet size, and how that's going to impact milk removal, and then suckling intensity. Let's go to the next slide. To remind you that, in fact, again, breeds that we have in North America and Europe, most of those breeds have what's called a very tight teat order. So this piglet only nurses that gland. It doesn't move around to nurse other glands typically. That piglet only nurses that gland, it doesn't move around. So once it establishes that teat order, that's the gland it always goes to. And what I'm going to try to convince you, is that means that physiologically, that gland, and that piglet now become a physiological unit. Because they're feeding off of each other in terms of the stimulation. We'll get back to that in a second. Next slide. We can start to see that manifested in a number of ways. One of those is the correlation between mammary gland mass, the mass of a gland a piglet is nursing, and the average state of the gain of that piglet. So this piglet, how fast does it gain, related to how this particular gland that it's nursing grows. That's the idea. Correlation, it's not certainly by no means perfect, but it certainly statistically significant, and several people have demonstrated that. So again, the idea that the average daily gain goes up, as the mass of the gland increases. Let's go to the next slide. So again, what I want to impress upon you is that what's happening in this gland for that piglet, is impacting the piglet. What's happening in the piglet is impacting the gland. The more milk this produces, the more milk is consumed by the piglet, the faster it grows. The faster it grows, it demands more milk from the gland, the gland is stimulated to grow. Again, these are unit, so it's why it's called a mammary gland piglet unit. So we gotta have to keep that in mind. And again, very much for these kinds of animals where that piglet is only nursing that gland. Other piglets nursing other glands are going to be the same kind of way. But we can think about what's happening between these two, and think of those as kind of a physiological unit. What we've just seen is this idea of piglet size playing into this idea of suckling intensity. So again, because of the teat order, we can talk about this piglet nursing this gland as being a physiological unit. The more it consumes the milk, the more it grows. It demands more from the mammary gland, the gland grows to accommodate that. Makes more milk, makes it grow faster, and so on. So again, this gets down to piglet size, and how that's impacting growth of the mammary gland, as well as milk production. Now I want to shift gear and talk a little bit about frequency of suckling. A couple of features that I want to share with you with respect to that. Let's go to the next slide. want to just remind you that every time the animal has milked or nursed, there's a surge of prolactin. It's a transient surge of prolactin, but a surge of prolactin nonetheless. So indicated for the dairy cow here. And again, in a 24 hour period if we milk her three times a day, you're going to see three of these spikes of prolactin, these surges of prolactin. And the pig, on the other hand, they're nursed every 45, 50 minutes, something like that on average. And so we see lots of these spikes of prolactin during the course of the day. And if you took the piglets away, it would take maybe a couple hours or so for this to go down to baseline. The prolactin surge, of course, is causing the mammary gland to refill because the piglet is empty. It didn't take out all the milk, there's still a bit milk left in the gland after nursing. But it takes out the bulk of the milk. And so the prolactin is helping that refill the gland. So, another question is, how fast does the gland refill? This is a study, interesting study, where people tried to examine roughly how this is happening, or how fast it's happening. So the idea is that at zero time, not very much milk is left in the gland. And then, what they did was, they said okay. Really what they did was, they said, at 50 minutes, that's our gold standard. So that's basically our 100%, okay. Then they also tried to estimate how much milk has been produced in a 35 minute period, or a 70 minute period, or a 100 minute period. And then comparing that to the 50 minute period. What you see, if you look at this graphic is, the gland actually refills very rapidly. So even after 35 minutes it's very close to being full, that is, compared to the 50 minute time period. And then it only increases by say 10%, up to actually between the 35 and the 70 minute time period. And that's really only about 25% higher here at the 100 minute. So again, this thing's flat lining. This curve is essentially starting to flat line here. So it's not accumulating a lot. The bulk of the refilling of the mammary glands is occurring during this first half an hour, 35, maybe 45 minutes, something like that. That's important in terms of frequency of nursing. So let's go to the next slide. What I've done here is to try to calculate, and give you an idea, what are we talking about here in terms of the effect on of nursing frequency on total milk yield? So if we assume at 35 minutes, if we assume, and this is just a number I pulled out of some data in terms of rough average of milk production. 45 ml of milk were removed from a gland per nursing. This number of minutes in a 24 hour period, so the 35 minute interval, so again, they nurse every 35 minutes. If they did that all the time during a 24 hour period, that's roughly 40 nursings per day, per 24 hours. Times 40 ml's is 1600 ml produced by that sow during that 24 hour period. On the other hand, if they nurse every 70 minutes, so basically, twice as long, you have half as many nursings. You're only getting about 10% more milk, and so there's a lot lot less milk. Calculates out to 880 ml per 24 hours. So you can see that those shorter intervals are important. So sows that have nursing intervals of an hour, or something like that, are ultimately going to give less total milk, than sows that may have maybe a 45 minute interval, or something of that nature. So clearly, nursing interval is important, and that's illustrated here. So again, as long as we capture the bulk of this early part of this curve, hopefully not nursing this short. They're hopefully not nursing much beyond say 50 minutes, then we're probably going to maximize the amount of milk that she produces in the course of a day. Now let's review very quickly what we've covered in this video. So just to remind you that the piglet size does affect mammary development and milk yield. We saw that in the couple of different ways. This idea, of piglet and the mammary gland are a physiological unit. So the piglet's removing more milk, that makes this gland grow more, provides more milk, makes the piglet grow more. And so we see this relationship going on there. So again, I've kind of called this piglet-mammary gland unit. The gland refills in roughly 40 minutes or so, something along those lines. So 40, 35, 40, 45 minutes. It's pretty much full to the point where if it goes much beyond that, you're going to get a lot less frequency of nursing during the course of the day. And then again, the idea that suckling frequency, or nursing frequency, affects total milk produced, and the total amount that's consumed in a 24 hour period. So we don't want those intervals to be too long in the case of the nursing piglets. [SOUND]
