Joan Cartan-Hansen, Host: Ancient and medieval doctors thought the stomach, not the heart or the brain, was the most important part of the body.

But they really didn't know how the digestive system worked.

Today, we have lots of different ways to learn about the digestive system.

And you might be surprised that some of them involves cows... (MUSIC) Gwinyai Chibisa, Associate Professor: Hey buddy!

Cartan-Hansen: Associate professor Gwinyai Chibisa and his team take care of these very special cows.

Chibisa: Learning about nutrition for cattle is important because we can determine what those requirements are.

And then once we know what those requirements are, then we can try to make sure that we formulate diets that are appropriate for those animals.

Cartan-Hansen: Cows are ruminants, as are other animals like elk, sheep and goats.

They have four stomach compartments.

When they eat, the plant materials are swallowed and then held in the first and the second compartments where bacteria and other micro-organisms start breaking down the food The first compartment is called the rumen and the reticulum.

Generally when the animal is resting, they bring the contents back up into their mouths.

This is called cud.

Ruminants then chew the cud again, breaking it down into a finer mush.

The food is then swallowed and moved to the first and second compartments for more digestion.

Next, the food moves into the third chamber or the omasum where water is taken out.

The omasum is also like a sieve.

It filters and send back to the rumen particles that are too big for further breakdown.

Finally, what's left moves into the fourth compartment called the abomasum where digestion is completed.

Chibisa: And so when we study what happens from that true stomach or the fourth stomach, all the way to what comes out of that end, uh, all, everything that happens in cattle is exactly the same as what happens in humans.

Cartan-Hansen: To test the impact of different types of diets on the nutrient supply, production performance, and health of these animals, Chibisa uses cannulated cows.

These cows have a surgically fitted cannula.

It's put in place after a hole is made in their first stomach.

It doesn't really bother the cow.

And these animals live a normal life ,except they get really good medical care and their food intake is carefully studied.

Chibisa: And so to just open the plugs, we just, uh, press inside.

Okay.

Then the plug goes in, and then we just grab it And at this point, we have access right into the rumen.

And, uh, and so as you can see, uh, we already have digestion in there.

So this is stuff they have been eating all morning.

Cartan-Hansen: During the digestive process, the stomach contents begin to ferment.

Microbes digest the fibers and some get converted into volatile fatty acids or VFA.

The VFAs eventually absorb into the bloodstream and are used as a source of energy.

Chibisa: Those canula, they're really important for us because it enables us to collect samples.

And then we use those samples to do research.

That ability to obtain samples is really good because then once we feed them something, then we can determine how much of that is digested, how much disappears, which then is important in terms of, um, knowing the nutritional value of different feeds that we have.

Cartan-Hansen: Chibisa collects some material from the cow's stomach to test for those VFAs.

Chibisa: And so, if you collect a sample, then you can determine the p-H in the rumen, which then can tell you what's happening in terms of digestion in there.

So, at this point, we can just close, uh, the, the cannulate itself.

So essentially you just put it in place and then we just push it inwards and it's closed after that.

Cartan-Hansen: Chibisa heads into the back to extract out the liquid in the sample Chibisa: So, we use really low tech stuff for that, your normal cheesecloth.

That's what we use to filter, uh, to obtain the sample.

So, uh, right in there, I have a small little cup to collect the sample.

I have my final, and then I just place, uh, the cheesecloth over.

And then I just tried to squeeze as much fluid as I can to obtain, uh, the sample we're gonna use today.

And so just squeeze a little bit in there.

And then once I have everything in there, and then just grab the ends and then squeeze.

So as you can see, the juices green in color, which is not surprising because they've been eating grass all morning.

And so the color of what you get is determined by what's in their diet.

And so at this point, uh, we have, uh, the sample ready Cartan-Hansen: He takes the sample and tests for the p-h level.

It's about right for as long as the food has been in the cow's stomach.

Next, he'll take the liquid to study the microbes found in the sample.

Chibisa: So, in terms of cattle nutrition, uh, there's still a lot to learn.

Uh, so for example, the biggest thing is, uh, in the rumen and we have a lot of microbes in there and we are still at a point where we don't really know, uh, what some of those microbes do Cartan-Hansen: Chibisa thinks if they can learn the best way to feed the microbes, they'll have found the best way to feed the cow.

And understanding microbes in the digestive system isn't just for cows Chibisa: In human nutrition, we now know that, uh, the microbial makeup, you know, a gut, uh, influences our mood, for example.

Cartan-Hansen: Chibisa's research is important because its impact is more than just learning what to feed cows.

Chibisa: We also have to worry about the environment because what we feed also impacts what comes out of the back end, which then can have an impact in terms of our climate, for example.

Uh, and so I, I would love if we had more people studying nutrition because, uh, as humans, we always need to have food.

And as long as we need to eat to live, then that means that, you know, we always have to raise animals.

We always have to have, uh, crop production as well.

(cows mooing) Chibisa: There's a whole world of, you know, science that's related to crop production, uh, and animal production.

And my encouragement is, yeah, we need to have more people come into the field because, uh, there's a lot.

We still don't know.

And, uh, there's a lot we can do better.

Cartan-Hansen: If you want to learn more about the digestive system, check out the Science Trek website.

You'll find it at Science Trek dot org.

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