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.
Mastitis Syndromes
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来自 University of Illinois at Urbana-Champaign 的课程
Lactation Biology
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从本节课中
Module 9: Mastitis
The mammary gland is an excretory gland, meaning that it produces a fluid that is secreted to the outside of the body. These secretions leave the gland through a series of ducts that eventually open to the outside of the skin. The presence of these openings not only means that the mammary secretion can leave the gland, it also means that microorganisms can enter the gland. When that happens, the gland may become infected and present as a disease known as mastitis. Mastitis is an inflammation of the mammary gland, the inflammation most commonly being caused by an infection by a pathogen. Mastitis is the most costly disease in dairy cattle, but is also prevalent in other species, including our own. We will examine many of the aspects of how this disease is manifested using the dairy cow as our primary example in this module. We will examine mastitis at the level of an individual cow, as well as at the whole herd level. And then to fully integrate and apply the knowledge gained about this disease, we will examine several real-life cases of herd-level mastitis problems faced by dairy producers.
与讲师见面
Dr. Walter Hurley, PhDProfessor Emeritus
Department of Animal Sciences
Welcome back.
We're going to continue our exploration of mastitis, again,
inflammation of the mammary gland.
So let's go to the first slide and
just kind of review just a couple concepts here.
And that is as we think about this very complex disease, we
need to keep in mind the host and again, the dairy cows are a model for this.
The agent, and
most of the time we're talking about some bacterium that's getting in the mammary
gland causing this inflammation, causing an infection in the environment.
Now, in this particular video we're going to talk about syndromes and
types of mastitis.
So how do we start to categorize different types of mastitis as a whole range of kind
of things?
Different syndrome that is responses by the host and so on.
And eventually that's going to lead us to integrating more of these things together.
But right now, we're just going to need to lay the groundwork for, again,
syndromes and types.
So let's go to the first slide here, next slide.
Again, mastitis syndromes.
We can start breaking this down in terms of clinical versus subclinical.
This is really the kind of level of response to the immune system in
the mammary gland to this external insult.
And again, usually that's caused by some sort of bacterium.
Prevalence, how prevalent are these?
Typically for clinical mastitis in a dairy herd, a dairy cow herd,
we're talking about 2 to 4% of the cows will have a clinical episode per month.
So if you have 100 cows, between two and four of those cows,
during that roughly 30-day period, will come down with a clinical mastitis.
So that's kind of the norm.
What's really kind of interesting is the fact that if we talk about subclinical
mastitis.
That anywhere from 15 to 40 times that many.
So for every two cows in that 100 cow herd.
Roughly 30 cows are going to probably have some sort of subclinical level and
can go up as high as 40 times as many.
So many, many, many more cows are going to have a sub-clinical level,
we'll define these here in a little bit versus the clinical level.
Clinical level again is really just what we're talking about is their external,
their signs you can clearly tell pretty easily that that cow has a pretty
bad case of mastitis or an inflammation of the mammary gland.
Subclinical, you've got to use certain tests or
certain kinds of indicators, usually looking at levels of somatic cells.
Those leucocytes in the milk to tell whether that cow has subclinical mastitis.
So let's start breaking this down and looking at the clinical mastitis.
And we can break this down in terms of different syndromes.
Again, different syndromes here of mastitis.
Subacute, acute, peracute and chronic.
And we're going to go through each of these individually to kind of give you
an idea of what you might expect if you found a cow with subacute mastitis or
peracute mastitis and so on.
So let's start with subacute mastitis.
[COUGH] Typically these are mild inflammations.
They may be no visible signs externally in terms of looking at the udder or
touching the udder, palpitating the udder.
But we do see oftentimes flakes or clots in the milk.
So as you strip the milk out of the tit, there's usually some flakes or clots.
So as the milk compositions change a little bit, and you're getting this,
instead of a nice fluid coming out, there are a few flakes or
clots coming out in the milk.
And sometimes, on occasion, the milk may have an off color to it.
Let's go to the next slide.
So, this is an example you have to look very carefully.
Right at the end of these red arrows here are a couple of examples of the flakes or
clots in milk that you would find.
And so typically, when if you're using something called a strip cup or
something like that.
Milk is white, the flakes are going to be white and
typically these things are black.
Sometimes people strip it out on a black mat under the cow.
Again you can very clearly and easily see these flakes or clots coming out.
Fairly typical for mastitis subacute mastitis, a fairly mild inflammation.
Let's go ahead and start looking at now at the acute mastitis.
Just a little bit higher level in terms of the syndromes.
Sudden onset, moderate to severe inflammation of the udder, so
you can actually palpate something.
You can see the udder is perhaps, feel that it's hot, it's warmer than the rest
of the udder or the rest of the quarters, it's red, it's very touchy.
The cow might try to kick you or something if you try to touch it.
So there are signs in the udder.
Fairly visible signs and clear signs that there's something going on there.
Decreased milk production and serous milk and, fiber and clots.
So we do get those flakes or clots.
But even sometimes worse than that.
So let's go to the next slide and see an example.
This is a heifer with mastitis and clearly this particular quarter
has an inflammation in it compared to the other quarter here.
So that's an acute mastitis issue than this particular heifer,
absolutely no question about it.
This is a pretty obvious one here.
Next slide, and again this idea of the serous milk, if it gets really bad,
you get this real stringy kind of milk, and kind of serous fluid.
So the organic components start separating out from the water component of milk and
so again, fairly typical of acute mastitis.
So the next level of severity, the next syndrome,
next level of severity of clinical mastitis is called peracute mastitis.
Again, very sudden onset, very severe inflammation of the mammary gland,
serous milk.
And a lot of times, you get, although you do get systemic
responses like increased respiration, or increased rectal temperature.
Those kinds of things in the animal.
This is particularly significant here.
Significant systemic responses.
A really sick cow, even to the point of where they might die.
So this is kind of the top end in terms of severity
of mastitis in terms of the peracute syndrome.
So our fourth type of clinical mastitis syndrome is chronic mastitis.
This starts to get a little bit kind of in between the clinical and
subclinical because it basically goes back and forth.
So, typically the infection or
inflammation persist in the mammary gland as a subclinical mastitis.
We'll get to that here in just a moment.
Again, there are no external signs.
Not necessarily flakes or clots in the milk.
There will be an increase to somatic cell count, but unless you test for that,
you really can't see, otherwise.
And this can persist for months to years, and
then periodic flare ups in the clinical.
So it might be acute or even sometimes peracute, but usually acute or subacute.
So she'd be going along very nicely for a while, subclinical mastitis,
elevated somatic cell count.
And then all of a sudden,
we'll have a clinical episode that would lead a clear up, she'll be treated.
Go back to being subclinical and then fire up, and so on, and so forth.
So chronic mastitis is again, just kind of switching back and
forth between these two types of two different syndromes of mastitis.
So final type of or final syndrome of mastitis that we're going to talk about is
something called subclinical.
And so here again, there are no gross inflammation,
you really can't see the change in the mammary gland.
No gross changes in the milk that you can see again,
what you find is that there's an increase level of somatic cells.
So let's take a look at that.
Usually precedes a clinical episode.
So usually there's some low level of inflammation, subclinical inflammation.
Can be of long duration.
Difficult to detect, because again, you can't simply look at something,
you can't just necessarily see flakes or clots in the milk.
So again, it's difficult to detect.
You have to do something, some sort of a test, basically one way or
the other to determine it.
Clearly it reduces milk production and decreases milk quality because again,
the idea that those leukocytes in the milk,
the increase of the somatic cell count are secreting hydrolytic enzymes.
You get less cheese yields and
all those kinds of things that we've talked about in previous video.
Again, often times this goes untreated because you have so many cows with it.
And you really can't treat it and get rid of it.
And unfortunately, what that means is a lot of times it acts as a reservoir.
So the bacteria are in the mammary gland, a lot of times they are contagious
bacteria, and therefore they will be potentially passed on to other cows.
So, you kind of keep on infecting other cows as what it amounts to.
This is a significant issue, and again, remember that there are many,
many more cases of subclinical mastitis than there are of the clinical mastitis
within a herd at any given particular time.
Let's go to the next slide.
So again, the real key here is, in terms of detecting this, is to find or
look at the somatic cell count.
So again, we just have some somatic cells, some leukocytes here,
macrophages, lymphocytes, and neutrophils.
And how do you do that?
There are a number of ways to do that.
One way is to look at a herd, so the bulk tank.
All the milk from the milk cows go into a bulk tank.
And very often,
you can then evaluate the somatic cell count of the milk in the bulk tank.
That, kind of the average of all the cows that go into that.
So, if you're milking a hundred cows, all the milk is going in there, and so you can
kind of keep track of whats the level of somatic cell count in that bulk tank.
And if it goes abnormally high.
Then that probably suggests that you have some sort of a subclinical issue.
DHI, DHIA, will give again, once a month they'll come out.
Test the cows.
Give you information on somatic cell count on cows.
And if you see cows that have a persistent high level of somatic cells.
Then you know that they probably have subclinical mastitis.
So you can take information like this.
This might tell you, the bulk tank might tell you, well,
I've got a problem in the herd.
My somatic cell count has gone up over the last few months, and
it's quite significantly.
I'm starting to lose money,
lose premiums from the plant that's paying me for my milk.
I've got a problem so we'll test the cows here.
And I say, okay, well I've identified several cows that have this issue that
have, these are my cows that have subclinical mastitis.
But I don't know which quarter they are.
I don't know what to potentially look at or what to treat.
And so one way to do that is by this California mastitis test.
This was developed quite a few number of years ago now.
And really also is doing is giving you a cow-side estimate of how many
somatic cell are in the milk from that cow from each of the four quarters.
And so you got four little dishes here.
And we'll describe this in another video.
This one particularly is a positive one as it turns out.
And so we say okay, if I'm going to do something about this in this
particular cow, that's the quarter I want to go and treat.
The other ones are probably okay.
That's another way of thinking about subclinical mastitis.
