Lactation and especially milk, which is the product of that unique mammalian process, are routinely encountered within our daily lives. Nevertheless, they often are poorly understood by many, even including many who are engaged in the business of producing milk. The overall course goal is to introduce fundamental concepts that form the basis for understanding the biology of lactation, the biology of the mammary gland, and the products of that important physiological process. As a learner in this course, you will be provided with a series of easily understood presentations that collectively will help you build a foundation for greater understanding of lactation. You will be able to engage with other learners so that you can extend your learning beyond the video presentations. Ultimately, you will be able to construct your own mental model for understanding the wide range of topics that relate to the biology of lactation. Upon completion of the course, you will be prepared to expand your knowledge and understanding of lactation from other sources and experiences as you pursue your individual interests. Before you start the course, I suggest that you identify a question or several questions about lactation that you already have on your mind. This could be from your own experiences, something you read about or saw, or something you have wondered about. Write down your question(s) and use that to help you decide how to engage with the content of this course. You might engage with the modules in the order they are presented, or start with a module that is of particular interest to you, or pick and choose modules in any order. I encourage you to engage in all of the types of learning activities that this course has to offer, including but not limited to, the discussion forums, quizzes, peer-review assignments, and concept maps and other learning aids.
Growth Hormone - Cows
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來自 University of Illinois at Urbana-Champaign 的課程
Lactation Biology
3 個評分
從本節課中
Module 6: Lactation
In this module, we explore the many facets of lactation as a complex physiological process. We will find that removal of the milk in the gland is critical to continued production of that fluid. The interactions between milk removal, the systemic factors stimulating the gland to produce milk, such as several hormones, and the local factors that inhibit further milk secretion are examined. Some of the effects of milk removal, as well as the absence of milk removal, are discussed in this series of videos. The responses of the mammary gland to milk removal provide a means of understanding the impact of management practices on lactation.
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Dr. Walter Hurley, PhDProfessor Emeritus
Department of Animal Sciences
[SOUND] We're going to continue
our conversation about lactation.
And looking at hormones that are galactagogues,
hormones that are involved in controlling lactation and modulating lactation.
In this particular video, we're going to focus on growth hormone.
Growth hormone has been associated with growth,
metabolism in the animal and lactation for a long, long time.
And it certainly is one of the galactopoietic kinds of hormones and
we're going to explore that in several different species here.
First though,
I need to remind you that growth hormone is also called somatotropin.
That's another name, they're identical, it's the same thing,
it's just two different names for exactly the same thing.
So sometimes we'll talk about growth hormone GH, ST for somatotropin.
They are identical.
So when you see things like bovine growth hormones,
sometimes that's abbreviated bGH which the same thing as bST.
And same way for say rat G growth hormone is the same thing as rat somatotropin.
Human growth hormone, hGH is the same thing as hST.
So sometimes we put small letter in front of that to indicate which species we
are talking about.
The other thing that has come along in relatively recent years is the idea of
producing some of these hormones by recombinant DNA technologies,
genetic engineering and those kinds of things.
In that case, if that were the case, if this was produced that way,
sometimes they put an r in front of that for recombinant bovine growth hormone,
recombinant human growth hormone and so on.
These have certainly been produced.
You might also see it here with regard to the using the somatotropin abbreviation.
So we're going to explore a little bit about the role of growth hormone
in controlling lactation.
And we'll get to that here in just a second.
In our first example, we're going to talk about cows, and
this work was done in dairy cows.
As you may be aware, recombinant DNA technology's allowed us to produce large
quantities of growth hormone as well as other hormones.
And that's been found to be very useful and fairly powerful
galactagogue or galactapoetic factor in dairy cattle to increase milk production,
as we're going to talk about very briefly here.
I just gotta give you an overview of that area.
So we have over here milk yield kilograms per day, weeks of treatment.
Typically what they do is they start a growth hormone treatment after,
just immediately after the peak of lactation.
So this would be a normal lactation curve of your average regular milk cow.
You go to the next slide what we see is if you start administering bovine
somatotropin here the formulas that are used commercially are often
two week formula, so you only have to administer it twice every other week.
We almost see like there is a second lactation curve on top of that.
So clearly, area under the curve,
is significantly higher,roughly 10 to 15% greater milk production
in those animals that are provided with bovine somatotropin.
And there are many many things that have been used in dairy cattle to try
to increase milk production.
And this is one of the few things that they found that's very, very consistent.
Doesn't seem to cause a lot of problems in terms of the animals.
You consistently get that 10, 15,
perhaps even a little bit more, milk production from the animals.
And we'll explore some other aspects of that, so
take another look at the next slide.
Again, this is used commercially now for quite a number of years at this point.
Some facts about that, it takes about a week to maximize the impact.
So once you start administering the bST or the bovine growth hormone, to the cows,
it takes about a week to maximize that or get the maximum benefit of that.
So it's not instantaneous, it take a little while.
We find that it does not affect milk composition, and as such,
it really doesn't affect manufacturing or cheese yield and things like that, because
they simply give more milk with the same composition, is essentially what happens.
And so you end up getting more cheese, but it's not changing the characteristics of
that cheese, or the other kinds of products that you might get from
fermented products, yogurt, and so on, and so forth from milk.
There really is not an increased concentration of bST,
that is the growth hormone,
in the milk itself, at least at the doses that are used in commercial systems.
If you give lots of growth hormone, then maybe you might see that.
But in the kinds of doses given to cows in commercial systems,
you don't really see an impact on the concentration of the hormone in the milk.
And let me take an aside here, and make an important point.
Every drop of milk produced by every
mammal since the first mammal started producing milk has had hormones in it,
including growth hormone, including somatotropin.
The mammary gland is an excretory tissue in the sense that anything in the body
of the animal that's lactating is probably going to be secreted to some degree or
another in the milk.
So, milk has always had hormones.
Every infant that ever nursed their mother,
every young that ever nursed their mother has been exposed to hormones in the milk.
The milk always has hormones in it.
So what we're saying here is that the normal amount of growth hormone that we
find in milk of cows, quote normally, is really not changed when we administer,
again these doses used in commercial systems here.
It does not appreciably affect internal like growth factor when in concentration.
So one of the mechanisms,
there are several mechanisms by which growth hormone works.
One of the mechanisms is it goes from the pituitary to the liver causing release or
secretion of IGF or insulin like growth factor one.
Which then goes to the mammary gland as well as other tissues, and
it impacts metabolism in those tissues, growth, muscle growth, lipid,
the adipose tissue, lactation and so on and so forth.
And it doesn't really particularly affect IGF concentrations in the milk,
again, administering this as we've talked about up here.
Does not affect the prevalence of mastitis.
The cows give more milk but the actual act of supplying this
hormone does not particularly affect the incidence of mastitis,
the prevalence of mastitis in dairy cows.
It does, on the other hand, require an increased nutrient intake.
So if we don't feed the cows properly, you can give all the hormone you want,
they're not going to make anymore milk.
So, it does take an increased level of management including nutrition,
and so very, very well managed cows,
this really doesn't have any effect other than, they give more milk.
So, again, you have to have the good management.
If you have poorly managed animals, they're not fed appropriately and so
on, then you're probably not going to get very much impact
by the growth hormone administration.
Couple other things here that sometimes people are considering, in this sequence,
amino acid sequences of the bovine growth hormone and pST or
pGH, would be porcine for pig, are very, very similar.
They're like I think 90% similar in terms of the amino acid sequence.
But they're pretty substantially different the sequence of human growth hormone.
So, that means that these hormones, porcine growth hormone,
bovine growth hormone.
If we ingest those, well, first of all,
a lot of it is going to be broken by the proteases in our stomach and
our intestine, but even beyond that, it's very, very, very low potency compared
to our own growth hormones coming from our own pituitary.
Again, binding to growth hormone receptors is very low, and again,
it should really have no effect on human growth.
Human muscle development, human breast development and
so on, as opposed to our own growth hormone.
That's really the key difference is here.
Sometimes people are using human growth hormone to bolster growth of muscle tissue
and so on and so forth in our own species.
[SOUND]
