[SOUND] Welcome, I'm going to talk a bit
about milk ejection. And remind you some things about milk ejection, especially with respect to the sow, I always find it very interesting because there's a number of aspects of this, I think, are very very different from the cow. One of those aspects though, relates to how sensitive the animal is to oxytocin release and to milk let down. So what I have here is, this blue triangle basically represents oxytocin release, so it's kind of representing generically, an increase of oxytocin, and then the oxytocin concentration declines in the blood. And we're talking about a few minutes here, we're talking about maybe five minutes. The threshold of the cow to this oxytocin release is pretty low, it doesn't take a lot of oxytocin to get them to let their milk down. So they're letting their milk down through an extended period of time, several minutes, go to the next slide. On the other hand, the sow has a very high threshold to oxytocin for her to let her milk down, go to the next slide. So we find that actual milk ejection is only lasting for say, 10 to 20 seconds, 15 seconds, or something like that, compared to 5 minutes in the cow. What that really means is of course, that those piglets have to be there and everything has to be very coordinated, otherwise they're going to miss a meal. If they miss this 15 second window of time, when milk is actually available to be removed from the gland, because of the milk ejection process. So we're going to examine this milk ejection process in a little more detail. One of the interesting characteristics of milk ejection and nursing, suckling, in this kind of a species, is the very somewhat complicated behavior processes that's going on. And again, I've always found this very, very interesting myself. So the sow and the piglet, piglets, the litter, are going through a series of kind of coordinated behavioral processes. So let's starts with the sow, the sow starts grunting, which kind of signals those piglets hey somethings going to happen, basically it's time for a meal. She will lie down, and roll over to expose both sets of the mammary glands, so they can get to the mammary glands. The piglets are going to be nuzzling the glands, trying to suck on the teats, trying to get something out, although again, milk ejection has not happened yet, so they're not getting any milk. She will start this rhythmic grunting about one per second, [SOUND] and then when that rhythmic grunting increases, the rate of that rhythmic grunting increases. That's approximate the time oxytocin is released from the pituitary, the posterior pituitary. And of course, it takes 25 seconds roughly for it to get circulated through the blood to get to the mammary gland, and start the process of causing milk ejection. So again, increase in grunting for 25, 30 seconds, milk ejection itself is only occurring for a 10 to 20 second period of time, say roughly 15 seconds. Milk removal is the only time they're going to get milk out, they're not going to get it out beforehand, they're not going to get it after milk ejection is over. Grunting subsides once the milk ejection process is over, and then typically she will roll over to prevent them from getting to the mammary glands. Or she will stand up to get away from them trying to suckle on her, and they usually then goes to sleep. So what I want to do is, I've got a video we're going to show you in a few moments. But I need to set this up, so you can see some of the differences, and what we're looking at, is we're looking at the piglets. You should be able to hear the sow grunting, so you should be able to hear the grunting. So you should be able to hear the rhythmic slow grunting, and then when she speeds up, and then if we're careful we can actually watch and see the behavior, what's going on in terms of the piglets. Until we're getting milk here, you're not getting milk back here, and then eventually in that video she stands up, and it's all over. So let's go ahead and go to the next slide, so I've got a couple sets of pictures here to illustrate this. Again to set it up, so the top picture is the pre-milk ejection, and then this is when during the 15 seconds or so, when milk ejection is happening. So we look at the piglets, they're on the teat, they're trying to suckle the teat, and they have typically more slow mouth actions trying to suckle on the teat. They can also be moving around a little bit, they're really not quite as focused. But when that milk's coming out, when actually milk ejection's occurring, they pull back on the teat, you can see they pull on the teat. The ears are flat back, and then the mouth is going much, much faster during the time period. Again, that's only going to last for a few seconds. Let's go to our next example, just another set of piglets, same concept, pre-milk ejection. They're on the teat, yes, but they are slowly trying to suckle that teat, nothing is happening at that point in terms of getting milk out. They really haven't pulled back yet, during milk ejection you see this animal has pulled back, this one particularly can see has pulled back on that teat a bit. The ears are back, they are very very focused, nothing is going to distract them during that 15 seconds or so, and again the mouth actions are much much faster. So, when you are looking at this video coming up, pay attention to those things, and I've tried to put in some captions to give you some hints about what's going on. It's about two, two and a half minute period of time, what's going on during each of those stages, so enjoy the video. Let's review now this milk ejection process, and what we've talked about. There's a sequence of behavioral interactions occurring between the sow and her litter that are going on. And from the video you saw, you only saw a fraction of what's going on between them, like in the massaging of the teats, the nuzzling of the teats, and the grunting the sow and so on and so forth, all those kinds of things. So, a lot of behavioral processes are going on there, between sow and litter, and how they come together during that period of time leading up to and during milk ejection. Remember that piglets cannot get milk, other than when milk is being ejected. So all that they can be sitting there, sucking on the teat, but nothing's happening, they're not getting any milk. I also point out, that there are what they call non-nutritive nursings, that is, they go through all the motions, but milk ejection doesn't actually happen. So they go through the whole process, or part of the process, and the milk ejection doesn't happen, they're unable to stimulate milk ejection. And there's a lot of reasons why that may be the case. So not every nursing bout is what you saw in that video. Milk ejection in the sow only lasts for a very short period of time. Again, very, very highly coordinated, going back to the behavior here. And also, to remind you that this massaging and nuzzling of the gland that you saw at the beginning of the video, is stimulating not only the release of oxytocin, but also the release of prolactin. Because that gland's going to be empty pretty quickly, and you need that prolactin then, to help stimulate refilling of the mammary gland. [SOUND]
