Monogastric
We’ll start with monogastric.
Monogastric animals have simple,
single-chambered stomachs. These
include pigs, dogs, rats, rabbits,
horses and humans.
A monogastric digestive system works
as soon as food enters the mouth.
Saliva moistens the food and begins the
digestive process. After being chewed
and swallowed, the food travels down
the oesophagus and into the stomach,
where acids and enzymes work to break
it down. Bile salts are stored in the gall
bladder and they are secreted once the
contents of the stomach has reached the
small intestines. This is where most of the
fat is broken down. The pancreas secretes
enzymes and alkali to neutralize stomach
acid.
Deer are slightly different as they don’t
actually have a gall bladder – they have
evolved so they don’t need one. Other
mammals that don’t have gall bladders
include elephants and whales.Ruminants
Ruminants include deer, tahr,
chamois, goats, cattle and sheep.
Instead of having one compartment to
the stomach like monogastric animals,
ruminants have four. These are called the
rumen, the reticulum, the omasum andthe abomasum. Of the four parts, the
rumen is the largest.
As we all know, deer eat grass, leaves and
other plant-based materials. These are
made of cellulose, which is a molecule
that monogastric animals cannot digest.
However there are microorganisms in
the ruminant’s stomach that can digest
cellulose. When a deer eats, it generally
feeds very fast and depending on food
availability and its nutritional value and
volume, it may take just one to two hours
to fill its stomach. This food is chewed
only enough for it to be swallowed
and is called the ‘first chewing’.
The first chamber that food enters is
the rumen, which is basically used for
storage. The rumen allows a deer to eat a
lot of food at once and digest it later. The
animal then brings the food back up into
its mouth and chews it again. Generally
it does this while resting. This process is
called ‘chewing the cud’.
The animal swallows the food again and
it passes to the second chamber of the
stomach where the cellulose digesting
microorganisms live. These organisms
attack the food and break it down in a
process called fermentation. The cellulose
then becomes a simpler substance that
can be absorbed by the animal. The
fermentation process produces methane
gas that ruminants must dischargeregularly – they do this by burping.
When they chew their cud again,
mixed in with the digested food
are the microorganisms. A lot of the
nutrition actually comes from these
organisms. This time when the food goes
down, it goes into the third chamber –
the omasum – where water is added to
the mix.
Finally the cud enters the last chamber- the abomasum – where gastric
juices continue the digestion. These
juices are like acid. Lastly it moves on
to the intestines. This is where the
food is absorbed by the animal’s body.
Interestingly, a Whitetail deer’s intestines
are up to 28 feet long when stretched
out! When the animal has absorbed
everything it can use, the parts that
are not digested are passed as waste
droppings.
Quite a complicated process. So what
does all this have to do with food
safety? Well, everything. The main causes
of infections that can lead to diseases
are through ingestion (eating) and
inhalation (breathing). Bacteria and toxins
are introduced these two ways, causing
potential problems.
Right, that’s about enough for now. Next
time I’ll discuss the other major
organs and the respiratory
system.
M
hb fhf h ll h d hbbSmall Intestine
Rumen
Omasum
Abomasum
Reticulum
Esophagus
Ruminant Stomach
August / September 2019 ~ NZ HUNTER MAGAZINE 73Monogastric
We’llstart with monogastric.
Monogastric animals have simple,
single-chambered stomachs. These
include pigs, dogs, rats, rabbits,
horses and humans.
A monogastric digestive system works
as soon as food enters the mouth.
Saliva moistens the food and begins the
digestive process. After being chewed
and swallowed, the food travels down
the oesophagus and into the stomach,
where acids and enzymes work to break
it down. Bile salts are stored in the gall
bladder and they are secreted once the
contents of the stomach has reached the
small intestines. This is where most of the
fat is broken down. The pancreas secretes
enzymes and alkali to neutralize stomach
acid.
Deer are slightly different as they don’t
actually have a gall bladder – they have
evolved so they don’t need one. Other
mammals that don’t have gall bladders
include elephants and whales.
Ruminants
Ruminants include deer, tahr,
chamois, goats, cattle and sheep.
Instead of having one compartment to
the stomach like monogastric animals,
ruminants have four. These are called the
rumen, the reticulum, the omasum and
theabomasum.Ofthefourparts,the
rumenis thelargest.
As we all know, deer eat grass, leaves and
other plant-based materials. These are
made of cellulose, which is a molecule
that monogastric animals cannot digest.
However there are microorganisms in
the ruminant’s stomach that can digest
cellulose. When a deer eats, it generally
feeds very fast and depending on food
availability and its nutritional value and
volume, it may take just one to two hours
to fill its stomach. This food is chewed
only enough for it to be swallowed
and is called the ‘first chewing’.
The first chamber that food enters is
the rumen, which is basically used for
storage. The rumen allows a deer to eat a
lot of food at once and digest it later. The
animal then brings the food back up into
its mouth and chews it again. Generally
it does this while resting. This process is
called ‘chewing the cud’.
The animal swallows the food again and
it passes to the second chamber of the
stomach where the cellulose digesting
microorganisms live. These organisms
attack the food and break it down in a
process called fermentation. The cellulose
then becomes a simpler substance that
can be absorbed by the animal. The
fermentation process produces methane
gas that ruminants must dischargeregularly– theydothisbyburping.
Whentheychewtheircudagain,
mixed in with the digested food
are the microorganisms. A lot of the
nutrition actually comes from these
organisms. This time when the food goes
down, it goes into the third chamber –
the omasum – where water is added to
the mix.
Finally the cud enters the last chamber- the abomasum – where gastric
juices continue the digestion. These
juices are like acid. Lastly it moves on
to the intestines. This is where the
food is absorbed by the animal’s body.
Interestingly, a Whitetail deer’s intestines
are up to 28 feet long when stretched
out! When the animal has absorbed
everything it can use, the parts that
are not digested are passed as waste
droppings.
Quite a complicated process. So what
does all this have to do with food
safety? Well, everything. The main causes
of infections that can lead to diseases
are through ingestion (eating) and
inhalation (breathing). Bacteria and toxins
are introduced these two ways, causing
potential problems.
Right, that’s about enough for now. Next
time I’ll discuss the other major
organs and the respiratory
system.
M
hb fhf h ll h d hbbSmall Intestine
Rumen
Omasum
Abomasum
Reticulum
Esophagus
Ruminant Stomach
August / September 2019 ~ NZ HUNTER MAGAZINE 73