Digestion
starts with the teeth, which cut and
grind up the food before it is passed down the oesophagus
and into the stomach. Occasionally
dry food will stick in the oesophagus, stopping swallowing,
and causing "choke". This is common with most unsoaked
sugar-beet nuts, and ponies that bolt their food.
The
stomach is the first part of the intestinal tract in the abdomen.
It lies against the diaphragm, and produces acidic secretions,
which start the chemical process of breaking down the food.
It is about 18 litres (4 gallons in volume.
From
the stomach, the food passes into the small intestine,
about 7 metres (22 feet) in length, and has a capacity
of about 65 litres
(14 gallons). Much of the food digestion takes place here,
before passing on to the caecum (not shown in the diagram)
- a large comma-shaped sac, about 33 litres (7 gallons) in
capacity.
The
large colon and with caecum act as ferminatation chambers,
allowing bacteria to break down the cellulose in the walls
of the plants that make up the herbivore's (plant eaters)
diet. The large colon is a 4 metres (12 feet long) "tube",
approximately 80 litres (17 gallons) in capacity. It runs
down the left side of the abdomen, across the pelvis, and
then suddenly decreases in diameter and doubles back to return
alongside its first half. This sharp bend is one of the most
common areas for impactive colic to occur. Food then passes
through the small colon, rectum and out on to the pasture.
Found
on the right-hand side, against the diaphragm it produces
bile (digestive ezymes), and is also responsible for many
biochemical processes in the body.
Present
on either side, immediately below the back bone, at the level
of the last ribs. Responsible for controlling body fluids
and electrolytes, and excreation of many waste products from
the blood stream and into the urine.
Found
on the left side of the abdomen. In the horse ( and to a lesser
extent the greyhound and camel) it acts as a major resevoir
of the red blood cells, which can be squeezed into the blood
stream when execising, increasing oxygen transfer, improving
performance.
Internal
parasites in the horse are commonly associated with colic.
In the stomach, bots (the larvae of several specie
of fly) over-winter, attached to the stomach lining. They
tend to concentrate around close to the outlet from the stomach,
and cause mechanical obstruction and very accute colic. In
the small intestine, roundworms (strongyles) are to
be found. Their larvae burrow through the gut wall, and migrate
around the body during development. They are associated with
spasmodic colic, but may also cause thrombosis in the blood
vessels. Tapeworms are to be found in the large gut
at the junction of the small intestine, caecum and colon.
Like bots, they may cause obstruction, preventing flow of
ingesta and setting up several different types of colic.
Parasitic
worms are very common in horses, despite modern wormers. Although
these kill a large percentage in the gut, a few will survive.
Immature larvae are often resistant to wormers, and rapidly
take the place of the adult to produce more eggs. The prolific
egg production of most worms ensure that there are always
plenty of worms on the pasture, so a horse can be easily reinfected.
One adult roundworm (Ascarid) may lay 200,000 eggs per
day!!! That is equivilant to 8.5 million between the six
week worming intervals. That is over 70 million eggs in one
year, from one worm, and the horse may be host to several
hundred such worms at anyone time!!! So keep worming!!
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