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Equine Digestive Anatomy

The topics this week will focus on equid nutrition. Understanding how and what to feed these animals is one of the most important aspects of basic care. We will start with digestive anatomy, how to evaluate your animal’s nutrient requirements, and then jump into feeding management. We will round out the week discussing colic and other nutritional disorders.

There are over 100 million horses, donkeys and mules in the world today and owners of these animals can be found on almost every continent and in almost every society. The Horse Course will cover many unique aspects of equine ownership and touch upon the science behind many of today’s management practices.

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Disease Management, Nutrition, Animal Behavior, Vital Signs

教學方

Chris J. Mortensen, Ph.D.
Professor

腳本

Alright, so welcome to week four, and this week

we're going to be talking a lot about nutrition, and I

just want to say thank you to everybody that's stuck

with the class so far, so mom, dad, thank you.

Hopefully you enjoy the rest of these

lectures and, you know, this week with nutrition.

going to try to bring some energy because nutrition can

be a really, really dry, dry topic and I

am going to try to make it as applicable as

possible, while slipping in some of the science with it.

And nutrition is such an important component of

taking care of your animal, so we will definitely

you know, go over that and, and what's

important to remember as a, as a horse owner.

So today, for this lecture right now, we're just going to

kind of talk some basic anatomy, of the horse digestive system.

And I think that will help you understand, you know, how

they digest these nutrients and why we feed them what we do.

So, horses are non-ruminant, herbivores, so herbivores eat, eat plants,

you know, plant material and, and that's what we feed them.

Now, a ruminant is what we call cows

and sheep and other livestock species like that.

Where they actually have this stomach, and in

cows they actually have four chambers to their stomach.

And that's where they ruminate, and they break down the plant material.

Well horses and pigs, and rhinoceros' and tapers that are, that

are very similar to, you know, they're relatives of the horse.

They are what we call monogastric, so they

have one stomach instead of four like the cow.

And this plant material that goes through

their stomach, into the small intestine, then

to the hind gut, that's where it's

fermented, and that's where it's broken down.

So all the stocks, and parts of the leaves, that don't get broken

down in the small intestine, actually get broken down in the hind gut.

So we'll talk a little bit about the, you know, anatomy and how that happens.

Now, if you look at the entire digestive system in the horse you can see

it takes up a lot of space in the body, I mean similar to us too.

This is all digestive system most of it with, with you know

we do have the, the lungs which you see there in that picture.

But then you have all of this digestive tract that, that's in there.

So, it's very, very large in the horse.

Now, when we talk digestion, we, we always start with the mouth

and then we carry it all the way through the digestive tract.

So that's really where, you know, your, your

digestive, digestion starts in the mouth with mastication.

And horses, when they chew, they don't chew up and down like

we do, they actually chew side to side, to break down these long

stem forages, remember this is you know, what nature intended for them to

eat was to eat the grasses and the other forages on the ground.

So, they produce a lot of, a lot of saliva, you know over ten gallons per day.

And get, you know of course that's going to vary on the forage, if its

really green leafy forage that's in the

spring, you know it's got more, more moisture

content so that they don't have to produce as much saliva as something like really

dry hay, or during the drier months

when they're eating grasses that are pretty dry.

They'll, they'll produce some more saliva and

that's important, it starts the digestion, digestion.

They've got some enzymes in there, and bicarbonate

which buffers the stomach, because remember all of us

know, you know, our stomachs can get a

little acidic, so yeah, that's what saliva helps with.

Now I thought it was worthwhile to talk about the teeth of the horse here.

And how we use this to, to age an animal, which we're going to get into.

Now in the horse, they can vary any where from 36 to 44 teeth.

Now 36 teeth are usually with mares, 44 are usually with stallions.

And the reason that is, is, is two sets of

teeth, there, we call them wolf teeth, and canine teeth.

Now typically, you only see those in the males,

so a stallion or a gelding are going to get these.

But sometimes, you can seen them in mares,

they'll actually get some of these teeth erupting.

Now, what's also interesting about this is, horses

do get baby teeth like us and they

only get 24, and by the time they're,

they're five, they should have all their adult teeth.

Now, in this table here, this is just showing you the diff-different times when

the baby teeth, so the deciduous teeth, actually come in, when you can expect it.

So when they're born, right away you can

see they, they have those front incisors, with those

young, young foals, and then by two and

a half years, their permanent incisors should be in.

Now, by the time a horse is five, so if we look here, that's when they

should have all of their teeth, all of

their permanent teeth should be in by then.

Okay?

Now, we talked a little bit about aging, so there's, there's different

ways to do it, and I'm just going to keep it brief for

this lecture, and talk about two main ways you, you can look

and, and open up a horse's mouth, and look at their teeth.

And the first is the angle of the upper and lower incisors.

See you can see the angle here with these really, really young horses.

Actually that angle is, is not quite 90 degrees

but, you know almost there, the, the it's pretty linear.

Now, as they get older, you can see this

older horse where you really get a sharp angle.

And so those, those teeth really start to, to protrude out and down.

Okay, and then the other way to tell an age, and this ones the easiest I

think is, is Galvayne's groove which here in

this picture you can see it really, really clearly.

Where, they start to get this growth down their corner incisor.

It's really just a, I'm a say it's a discoloration of the tooth.

And it starts to appear about the age of

ten, and then it starts to grow down the tooth.

So, if we looked at these images here

around age 10, that's where it first shows up.

Now by the time that are 15, that should be almost half way down the tooth.

So, you can see that and so if you look at this image here on a, on a real

horse you can see that it's a little past the

halfway mark, so this horse is probably 15 or greater.

Now, as they get older, towards 20, it almost hits the bottom of the tooth.

And then we see, around 25 to 30, it starts to recede down.

So there's still a little remnant of Galvayne's groove

on a 30 year old horse, and, you know,

as it recedes down the tooth and if you open an, you know, the mouth of a horse.

And you don't see galvayne's groove, but you see this huge,

you know incisive angle you know that's a pretty old horse.

So, those are the two ways that, that are

most common [COUGH] to age a horse by teeth.

So, I'm moving down from the mouth, the feed is carried down by the esophagus.

It takes it's food balls mix you know, with saliva it carries it

down, which is pretty long, four and a half feet, into the stomach.

Now, the stomach is really small on the

horse compared to the rest of the digestive tract.

It actually is only made up, you know, about 10%.

And again, when we talk about, you know,

we talked a little bit about behavior last week.

In horses, in donkeys, in mules, in all these other equids,

even zebras today, are meant to eat small meals all day.

So they go and eat little meals, and so the food,

it carried in the stomach, it doesn't need to be large.

It's where cattle or some of these ruminants, they go and

eat large meals, and then they go and sit under a tree.

And they'll chew their, their cud, reswallow

it, you know, regurgitate it, chew some

more, mix it with the bacteria in its stomach to digest that long forage.

That is not true with the equids, they, they eat this forage, it gets

in the stomach, gets mixed a little bit, and then gets passed on pretty quickly.

So, we can actually see that the, the, the feed actually passes

within like 15 minutes or less, it can be out of there.

Now, it's also interesting about horses, is horses cannot vomit, like

cows can, or even or dogs and cats and, and other pets.

Because they have a really tight sphincter between the esophagus and the stomach.

So, so that prevents them from, from vomiting.

And like I said, that feed is in there you know, 15 minutes,

roughly it gets mixed, and then it gets passed on to the small intestine.

Now, the, the small intestine is, is really long, 70 feet or 21 meters.

So, you know, if you look at a seven story building, and took it from the bottom

all the way up to the top, that's about

long the, the small intestine is in a horse.

And this is really important because this is

the, the major site of digestion and absorption.

So, this is where a lot of, the horse gets it's nutrients.

Things such as proteins, carbohydrates, vitamins, minerals, all of these

get, get broken down and absorbed in the small intestine.

Now.

[BLANK_AUDIO]

The [INAUDIBLE] really and it sticks with the, the plant material.

The plant material that is not broken down or

digested in the small intestine, gets passed into the cecum.

So the cecum's kind of a large vat, you know, getting this hind gut, and

you can see it's, it's very similar to the stomach of a cow or the rumen of a cow.

This is where that forage is, is getting mixed with the bacteria

that break down, with the microbes that break down the plant material.

And then it gets some more nutrients in it's diet from there.

Now, I will say here too, this is you know, we talked about laminitis.

When a horse, or a donkey, or, or other equid, goes and eats a lot of

grain, so they go and they just eat grain, grain, grain, grain, as much as they can.

And that large meal gets in their stomach and is passed on to the small intestine.

Well a lot of that grain doesn't get digested

in the small intestine, so they empty into the cecum.

And this is where that, that those microbes just

go crazy, that's what we talked about in laminitis.

So, that's why we see that happening.

Now normally, when we feed a grain, you know,

either five pounds or less per meal, that grain

will get di, most of it will get digested

in the small intestine and we're not worried about it.

It's just these horses that get into the, the feed bag and eat themselves.

Now, the, going on from the cecum we go into the large colon

and this is huge ,where you can see 20 gallons or 75 liters

and, and so this is where those microbes broken down those nutrients, gets

passed on to the large colon, and these are where these are absorbed.

Now, I also put this in here because I, I

talk later in the week, is going to be on colic.

And this is where we see a lot of impaction because of the twists and turns.

Again, we're feeding these, these horses and donkeys, you know, twice a day,

you know, maybe three times a day, so they get these large meals.

They get large, you know, a meal of hay,

and then that gets passed on in the digestive tract.

So what happens is, when you get to this large corn,

that large meal can get stuck at these pelvic fractures, where they,

they, it gets in and it just, you know, it can't

turn, and this is where, and then it gets all backed up.

And so, this is where we see a lot of impaction colic, in the equids.

Now, after the large colon, the, the small colon, the rectum

gets a little bit, you know, smaller in the digestive tract.

And this is where a lot of the water's absorbed from the diet.

So, all of that plant material, that had

a lot of moisture, that's where it's absorbed.

And this is where it forms those fecal balls that we see with horses.

Now, during the spring, anybody that, that

owns any of these animals knows, during the

spring, when, when the forage is really rich

in moisture, and you really green, the small

colon probably can't absorb all that water,

so their, their feces is a little bit

more watery than, say, late summer, or in

the winter, when they're eating more dry forage.

So, that kind of covers the, the digestive system.

And in the next lecture, we're going to

jump into, you know, talking about body condition,

how to weigh your horse, if you don't have a livestock scale, stuff like that.

So, I look forward to seeing you in the next lecture.

[BLANK_AUDIO]

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