[NOISE] Let's go to the next set of definitions. This really relates to the product of the mammary gland, and so we have mammary gland secretions as kind of a general term. That encompasses all of these fluids that may be removed from the milk via the teet or nipple. The composition and quantity of this varies considerably among species and it's an indication of the functionality of the state of the mammary gland. So colostrum, first milk of the mammary gland, has a different composition than milk. And then we're going to talk about transition milk here, and the part in between there in a second. So the mammary gland functionality is changing, the physiology of the gland is changing from one to another stage. And that's reflected in the product that's coming out of the gland. So milk is produced during lactation. White liquid consisting of water, lactose, fat, protein, minerals, and vitamins, this is the fluid that we normally think of as milk. Colostrum is the mammary secretion, the very first mammary secretion coming from the mammary gland after the young are born. Colostrogenesis is a word that we think of in terms of formation of that colostrum, because that's occurring actually prepartum, prior to parturition. It's associated a bit with lactogenesis, the early stage of lactogenesis. Transition milk, so we have colostrum composition very, very high, typically in immunoglobulins and variety of other kinds of things. And then we have milk, which is again, the fluid we most normally think of, and the composition of this product in between is typically referred to as transition milk. And how long that takes depends upon the species? It depends on the physiological states of the animal, so on and so forth. So these are some different kinds of ways of thinking about the product that's coming out of the mammary gland. Just to give you a few other definitions here, at the end of lactation, when milk is no longer removed from the gland, so one of the keys in maintaining lactation is that you have to remove milk from the gland. One way or the other. If we stop that then the mammary undergoes involution. A regression of the mammary gland, a regression of the mammary function, it's no longer producing milk. And very, very typically in most species, you get a regression of the structure, and again this transition from a lactating state to a non-lactating state. Galactorrhea or sometimes referred to as lactorrhea, is the spontaneous flow of milk from the breast. Again, this is a term often, most often used for humans. So that's again, why we're using the word breast here. Spontaneous flow of milk from the breast, usually not associated with childbirth or nursing. So it's not normally associated with normal lactation in women. It's occurring because something else is causing milk to be secreted from the breast of the woman. And again spontaneous flow from the breast. Again not associated with childbirth and nursing. It's fine to use this term for other species as well, but typically you find that associated with human lactation. Galactagogue is pretty much any substance that promotes lactation. Lots and lots of different things can promote lactation in animals often altering in general. Many times these galactogogues are altering the hormonal control of mammary gland and the lactation process one way or the other. And there's a variety of different kinds of substances that do this, there's a variety of different mechanisms by which they would do this. So if we kinds put all these definitions together, think about lactation biology, it involves the production of milk. Development and function of the structure and function of the mammary gland. Metabolic and reproductive status of the female. So things that go into this, nutrition and so on that go into this for the female. And developmental status of the nursing young. Because as the mammary gland changes, the nursing young is also changing. So there's this relationship between milk removal, because except, for dairy animals where we might use a machine to remove milk, the young are the ones that are actually removing the milk. And kind of having an impact on what that lactation process is all about. Lactation is a characteristic of mammals. And the key to remember is, it's part of the reproductive strategy of all mammals. A really important part. So what I want to do is to kind of give you an idea of how to some of the definitions that we started with here a few moments ago. And how those fit in to overall view of reproduction in female animals at least. So let's take a generic view of reproduction, lactation, and some of the things that we've talked here over the last few minutes. Females Start with estrous cycles. Somewhere along the line, if they become pregnant, conception. Pregnancy here, indicated in this bar. Fetal development's occurring during that period of time. So we're really talking about the offspring here and the physiological process in the mother here in this big arrow. She gives birth or as you'll see later on, in some species they actually, some mammals actually lay eggs and they hatch the eggs. Parturition is occurring, and then you have neonatal growth. Neonatal Development is associated with this lactation, this lactation process. So in mammals, intrauterine. And again this can be vary considerably in terms of how long this is. The young are born or, in the case of as you'll see later on monotremes, they hatch, they eggs hatch. And then extra uterine development, you can think of that as what's going on here. So this continued investment by the mother in development of the neonate. We have lactation here. So let's go back and look at some of those terms we started out with. So mammogenesis, mammogenesis actually starts way back here when the mother is a fetus and goes on through different kinds of stages. During pregnancy we see a tremendous growth in the mammary development. So again a lot mammogenesis occurring here, and this line actually extends past parturition because very often the mammary gland continues to grow, even in early lactation. Lactogenesis, I've kind of put here and associated with parturition. This going from a nonlactating state here to a lactating state here. Again, this process of initiation of lactation is occurring during this timeframe. And then once lactation has started, you have to somehow keep it going. And typically, it's removal from the mammary gland by the neonate, or in dairy animals by a machine that's allowing us to maintain lactation. So this is kind of how these kinds of things fit together. And as we explore other modules and so on we'll start to realize, well yes, this is happening, but you don't necessarily have to have these kinds of processes occurring when the animal is, in fact, pregnant. But we'll explore that later on. So we've gone over a number of definitions of things. But I think it's important to kind of keep in mind what these definitions are. because they'll help us understand how to organize in our minds certain kinds of physiological characteristics of animals, structural characteristics of animals, thinking about milk and how milk changes and so on. So let's make sure that as we progress through this course that we keep these definitions in mind. [NOISE]
