Colic In Horses

The term "colic" means only "pain in the abdomen" or "pain in the
belly." There are many causes for such pain, ranging from the
mild and inconsequential to the life-threatening or fatal. One of
the problems with equine colic is that it can be very difficult
in the early stages to distinguish the mild from the potentially
fatal. This is why all cases of abdominal pain should be taken
seriously right from the onset

Once food has been chewed, it passes down the esophagus
("gullet") into the stomach. The horse has a fairly small stomach
for its size (8-15 litres), a design well suited to an animal
which grazes almost continuously in its natural state. After a
period of digestion in the stomach, food passes into the small
intestine. This part of the gut is approximately 22 m in length,
with a diameter of 7-10 cm, and a capacity of 40-50 litres.

The majority of the small intestine hangs from a curtain-like
membrane called the mesentery*. The messentery is attached to one
point in the middle of the abdomen under the spine. (The small
intestine looks like a very long sausage running along the bottom
of a thin net curtain, with the top of the curtain all bunched
together.) At the junction of the small and large intestines the
equine GIT has a large blind-ended* outpouching over 1 m long
with a capacity of 25-30 litres. This is the caecum (the horse's
version of our appendix). Food passes from the small intestine
into the caecum before passing into the large intestine.

Together, the caecum and large intestine form the horse's
"fermentation chamber," allowing it to gain nutritional support
from the complex carbohydrates contained in grasses and other
forage. Three to four metres long with a diameter of 20-25 cm
along most of its length and a capacity of over 50 litres, the
large intestine fills a significant part of the abdomen.
Surprisingly, this large unwieldy structure is tethered to the
body wall at only two points*: at its beginning (where it joins
the small intestine and caecum) and at its end (where it joins
the short, narrow* small colon). With
only two immobile points, the large intestine lies in the abdomen
in a neatly-arranged double-U formation, one "U" stacked on top
of the other. This arrangement entails the food making it around
a number of 180° bends* (known as "flexures") in the intestine.


Major Types of Colic

Impaction Colic:
This is the term used when the intestine becomes blocked by a
firm mass of food. Impactions most commonly occur in the large
intestine at one of the flexures. This is a fairly common type of
colic which usually resolves relatively easily with appropriate
treatment. However, an impaction may be just the first obvious
sign in a more complicated case.

Gas colic:
Sometimes gas builds up in the intestine, most commonly in the
large intestine and/or caecum. The gas stretches the intestine,
causing pain. Gas colics usually resolve fairly easily with
appropriate treatment, although it is essential to ensure that
there is no underlying reason for the problem.


Spasmodic colic:
Some cases of colic are due to increased intestinal contractions,
the abnormal spasms cause the intestines to contract painfully.
These cases usually respond fairly well.


Displacement/volvulus/torsion ('twisted gut'):
In a "displacement", a portion of the intestine has moved to an
abnormal position in the abdomen. A "volvulvus" or "torsion"
occurs when a piece of the intestine twists. The suspension of
the small intestine from the mesentery (the "net curtain") and
the unfixed nature of much of the large intestine predispose
horses to intestinal displacements and torsions. Except in rare
cases, these types of colic cause a total blockage of the
intestine and require immediate surgery if the horse is to
survive. In the early stages of a displacement/torsion colic, the
signs may be similar to those of a horse with one of the more
benign causes of colic. That is why it is important to take all
cases of colic seriously, and to seek veterinary advice at an
early stage.


Enteritis/colitis:
Some cases of abdominal pain are due to inflammation of the small
(enteritis) or large (colitis) intestines. These are serious
medical cases and require immediate veterinary attention.

Gastric distension/rupture:
When a horse gorges itself on grain or, even more seriously, a
substance which expands when dampened like dried beet pulp, the
contents of the stomach can swell. The horse's small stomach and
its inability to vomit mean that in these circumstances the
stomach may burst. Once this has happened death is inevitable. If
you suspect that your horse may have gorged itself on concentrate
feeds, seek veterinary advice immediately.

"Unknown":
In many cases of colic it is impossible to determine the reason
for the pain. Symptomatic treatment, close monitoring and
attention to any adverse developments usually lead to resolution
of the problem.


Signs of Colic

The signs of colic in horses range from almost imperceptible in
mild cases to extremely violent in severe cases. The following
list includes the most common signs:
lying down more than usual
getting up and lying down repeatedly
standing stretched out
standing frequently as if to urinate
turning the head towards the flank
repeatedly curling the upper lip
pawing at the ground
kicking at the abdomen
rolling


What to Do:

The severity of the case will dictate what you do when you find
your horse showing signs of colic. If he is behaving violently
call your veterinarian immediately. Violent behaviour usually
equates with great pain which usually equates with a serious case
of colic. Time is of the essence here. Not all horses show the
same severity of signs with the same type of colic, though, and
some horses may become quite violent with a relatively "mild"
case. If the signs of pain are less extreme, you can take a few
minutes to observe the horse's appearance and behaviour before
calling the veterinarian.

If possible, take his temperature, pulse and respiration rates.
Note what his appetite has been like in the past day or so, and
the consistency and frequency of defecation.
Has his water intake been normal?
Are his gums a normal colour?
Think about whether he has had access to any unusual feedstuffs
in the past day or so, whether any medications have been
administered, and whether there have been any changes in
management.


Now call your veterinarian. It is important to take all food away
from the horse until the veterinarian arrives. If he is nibbling
at his bedding, find a way to prevent this. Walking the horse can
be a useful way of distracting him from the pain, but he should
not be walked to exhaustion. If the horse insists on rolling,
there will be little you can do to prevent it. If possible, try
to get the horse to an area where he will do himself the least
damage when he rolls. But do not get hurt yourself. Do not
administer any drugs until your veterinarian has seen the horse,
unless he/she tells you to do so.


Prevention of Colic

If you happen to be a horse, colic is probably an unfortunate
fact of life. Annual colic incidences of approximately 10% are
quite common. Listed below are some of the management factors
which are thought to reduce colic incidence. Horses which fall
into high-risk categories, such as stabled horses in intense
training and fit horses recently injured, should be monitored
particularly closely.


allow as much turnout as possible
maintain a regular feeding schedule
ensure constant access to clean water
provide at least 60% of digestible energy from forage
do not feed excessive digestible energy
do not feed mouldy hay or grain
feed hay and water before grain
provide access to forage for as much of the day as possible
do not over graze pastures
do not feed or water horses before they have cooled out
maintain a consistent exercise regime
make all changes in diet, exercise level and management slowly
control intestinal parasites and assess efficiency periodically

By Janet Douglas, M.Sc., Ph.D.
Equine Research Centre
Guelph, Ontario, Canada