0:23
In our livestock based food productions, an important element
is how those animals take those plant based components and
convert them into products that we find palatable and digestible?
Taking care of nutritional feeding is so important, because it comprises
such a significant proportion of the cost of our production and
that's true for all of our systems.
But the actual proportion varies depending on the species and
depending on the type of system, and the consideration.
How much nutrition contributes and how much it costs depends on those things.
Dairy cattle, for instance, that are raised somewhat a pasture.
Nutrition might be 50 to 60% of those costs.
Whereas with pigs, it might be 80% of the cost of production in a swine system.
But because of these costs optimizing the nutritional content and
matching it with the production outcomes is a essential part of the management of
running of an efficient, effective and profitable system.
Because the costs are such a high proportion of the total costs that
go into an animal and nutrition, feeding an animal isn't just simply
turning them out onto a pasture or putting feed in front of them.
Nutrition is a complex, scientific process.
Feeding the animals exactly the right constituents at exactly the right time is
really important for the sustainability of production.
And to understand nutrition to be able to design good nutritional programs,
you need to be able to understand not just the components of the nutrition,
not just what the components of plants are and how they're made up,
but also the anatomy and physiology of the animal.
How their intestinal tract works?
How they digest nutrients?
How they maximize those to become most efficient in production?
So I'm Dr. Brian Aldridge,
I'm here at the College of Veterinary Medicine at the University of Illinois.
We're in the Department of Anatomy and to start to understand that science of
how nutrition works, we're going to go inside of a cow.
2:37
This is a skeleton of an adult cow that's used here as an anatomy demonstration to
teach the veterinary students.
The structures that are inherent to the function of this animal and
we want to just show you where the major part of the digestive system sits.
For ruminants, they're unique,
because they have four compartments to their stomach.
And within their abdomen, they have a massive fermentation vat called the rumen.
That's the second of the stomachs and it sits right here within
the belly of the animal, and all of the other structures
are secondary to really this rumen in the digestive process.
The rumen lining has small little papillae.
Little leaves, tiny little microscopic leaves,
which increase the surface area of the rumen.
And therefore, optimize its absorptive capacity.
Absorbing the breakdown products of the bacterial fermentation, particularly
the breakdown products of carbohydrate metabolism, the volatile fatty acids.
And that is the seat of efficiency for nutrition and the seat of efficiency for
production, as far as nutrition is concerned.
3:54
So here I am, holding the four stomachs of a ruminant inside the abdomen of this cow.
So, that's exactly where it sits.
But if you think this is the real structure and this is the real size,
I'm fooling you, because this is actually a sheep's stomach.
And it's about a tenth of the size of that,
which would sit inside this cow's abdomen.
Now, this is the real rumen of this animal.
And as you can see, it's massive.
It's a massive fermentation vat.
Probably all together, this structure holds
something like 300 liters of fluid.
Each compartment structurally designed both in its form and
its function to most efficiently, take indigestible proteins and
carbohydrates and make them digestible.
Firstly, for the animal and then to convert them into metabolic products.
5:02
The ruminant is unique in that it has four stomachs.
This here is the first stomach, it's called the reticulum.
The reticulum is in some ways, the first compartment that the food meets.
The food comes down the esophagus, down the throat and
through a small sphincter here and is then dumped into this part of the stomach.
It's lined with a reticulated mucosa, which is designed to capture particles and
it's so effective that if the animal swallows a piece of wire.
To prevent the wire from accessing lower parts of the intestine,
they get trapped there.
Stones will get trapped in this honeycomb appearance,
stopping its interference with other digestive processes.
And every part of this remarkable stomach system is unique in structure,
but also in lining.
And also, in its contents.
Each of them though, contiguous perform a different function,
because of their anatomical structure.
But this is also the part of the stomach when the food is chewed again and
again, this is the food that goes back up into the mouth.
So, a ruminant doesn't just chew its food once.
It takes in the food, it goes down into the reticular rumen and
then it's brought back up and down, so
that this plant material is in a stepwise fashion crushed and broken up.
And this occurs by a repeated process of chewing of swallowing,
of entry into the rumen vat and then of bringing it back up.
6:40
So, this is where rumination takes place.
This is also the first sac of this fermentation vat and food moves from this
structure into this large multi-sacked parts of the stomach called the rumen.
This is where all the fermentation takes place.
Again, it has a unique structure of sacks,
because that's where most of the mixing takes place.
It is mixed up, so that the bacteria are exposed to every part of
that digester and there's three layers of food in this rumen.
There's the top layer which is the gas, which is a byproduct of digestion.
There's a fiber layer that sits in there and that's the part of the fiber that goes
into the reticulum and is rechewed, it's the long fiber.
And then at the bottom, there's food particles suspended in liquid.
Looks more like pea soup.
And that's where the bacteria are doing most of their work being exposed to
the small fibers and doing the digestion,
taking the plant proteins and the complex carbohydrates and
breaking them down into simpler proteins and simpler sugars as well.
Probably, about 1.5 billion bacteria live in that in the animal.
From there, as the food is broken down, the more liquid component goes
through another sphincter, another opening into this omasum.
And every stage of digestion,
the particles are going from long fibers to smaller fibers.
And when it gets to there,
it's essentially smaller particles with a large amount of fluid.
But to get down into the smaller parts of the intestine in the lower parts of
the intestinal tract, most of the water should be removed and
that's what takes place in this omasum.
The lining of the omasum is like book leaves and
it's a perfect way to increase a surface areas such as, so that water
absorption could be maximized and that's where a lot of the water is absorbed.
8:47
From there, the food goes into what is really the true stomach, the abomasum.
The stomach that in humans and in pigs, and in horses does most of
the digestive processes of the gastric part of the intestine.
It's the true stomach, because that's where some of the enzymes
are produced that digest some of the carbohydrates and the proteins.
The lining of the abomasum is glandular.
It's full of folds, but it's secretory.
The only part of these four stomachs that secretes anything.
It secretes the digestive enzymes.
It secretes the hydrochloric acid to lower the pH.
It's a true stomach, because it's acidity,
it's pH is much lower than the rest of the intestinal tract.
The secretion that comes out of the lining of this is hydrochloric acid,
as with humans and as with other monogastrics.
So, the components of this part of the digestive tract have been
simplified from the long fiber that we've seen in the rumen and
the bacteria in the rumen have done most of the digestion.
They've been breaking down the celluloses and the starches to more simple sugars.
They've been taking the protein in those plants and
breaking them down into their essential acids.
In fact, the bacteria then take the amino acids and
put them into the protein of their own body wall and
they form part of the nutrients for the lower digestive tract.
The abomasum's role and the lower intestine is to take those bacteria,
and break them down, and to release the nutrients that they have released
from the grasses, and the grains that took place during the fermentation process.
So in some way for the ruminant,
the bacteria become an important dietary component.
The bacteria break down the plants and then the rest of the body digests
the bacteria, but there's things that we do nutritionally and managementally,
which affects the structure and function, the contents of these rumen.
If we don't get the nutrition right,
then we mess up the function of this wonderful organ.
And therefore, we decrease productivity.
[MUSIC]
Dr. Jim Lowe, DVM, MS, Dip ABVP (Food Animal)Associate Professor
Dr. Brian Aldridge, BVSc, MS, PhD, Dip ACVIM (Large Animal), MRCVSClinical Professor
