BIO2242 – LECTURE 8
What does this animal eat?
Food types – vegetation:
They have a protective cell wall which makes it difficult to digest
Vegetation as food:
The energy you want to get is bound up in molecules of cellulose, and there are
no vertebrates that can produce cellulose themselves. Many plants produce
secondary chemicals that inhibit the digestion of many materials within the cell.
Vegetation is low food quality and low assimilation efficiency, so it takes a long
time to get the energy out of the plant and a lower proportion of the amount of
food that you eat is able to be incorporated into your own body.
Protective cell well:
In order to break the protective cell wall, most herbivores have complex
Selenodont = half-mooned shaped, crescent shaped on each tooth. In herbivores,
the two jaws come down at the same time, so the teeth on the upper and lower
jaws meet at the same time.
Herbivores have reduced temporalis muscles (muscles at the top, that pull
upwards) and large massatar muscles, which are muscles that pull to the side.
They chew by moving their lower jaw sideways.
Difficult to digest:
The sheep is a foregut fermenter, it has an enlarged stomach, with many
compartments, it has a very long midgut, a relatively large hindgut with a lot of
The pony is a hindgut fermenter, it has a small stomach, mid gut is relatively long
but the hind gut is huge. Great expansion of the length of the gut which allows
longer digestion time and allows them to hold more food.
The cellulose, the main constitute in plant’s cell walls, need to be broken down
with enzymes that vertebrates don’t have. This is how we create carbon dioxide,
water and energy:
We need a fuel into that, so glucose is that fuel that goes into the chemical
reaction. If you had starch, these are glucose molecules that are joined together,
and we need get to glucose out of it, so we need amylase to take the starch, which
breaks down the separate glucose molecules, and the glucose then goes into the
reaction to extract energy from that (ATP).
In cellulose, it has a similar but different chemical bond. We want to get glucose
out of it but vertebrates don't have the enzyme. So we have to use the bacteria
that produce the enzyme, cellulase, that then, breaks down into glucose. The
glucose is then fermented to produce short chain fatty acids, where SCFA then go
into the oxidative-productive process to produce energy.
Bacteria produce cellulase -> SCFA which are molecules that go into the chemical
reaction to break down ozygen. Cellulose fermentation II:
They enlarge the region of the gut to be able to fit more bacteria and food in.
Herbivores digestive strategies:
Some of them get their energy from the microbial cell wall, so they are
fermenting the cellulose on the outside of the cell. And this happens in the
foregut hence foreut fermenters.
The other type is, instead of concentrating on fermenting the cell wall, we break
open each cell, which leaks the cell contents and digest those cell contents. And
so, they do ferment but only a small amount in the hindgut, hence hindgut
There are many foregut fermenters that ruminate. Rumination means that they
take a piece of grass and they chew it and they swallow it. This starts a softening