Why Cant Horses Throw Up

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					Why Can’t Horses Throw Up?


Shanna Hlady
Melissa Kozakewich       First, in answer to the question, “Can horses throw up?” NO, they
Lindsay Paulsen      cannot throw up. But did you ever wonder why? Well our team at the
                     University of Alberta has researched this question and came up with a
                     detailed response.
                         When a horse first ingests food, it is swallowed through the mouth
                     cavity and is passed down the esophagus. Horses have a strong band of
                     muscle around their esophagus at the entrance to the stomach, called the
                     “cardiac sphincter” also referred to as the “esophageal sphincter”. The
                     cardiac sphincter is actually the strongest sphincter muscle of all species.
                         The cardiac sphincter exists in all mammals at the top of the
                     stomach, and in the horses it differs from other mammals because of its
                     extreme strength and inability to relax and allow the horse to throw up
                     like other mammals. As stated by Dr. Susan Novak, the AAFRD(Alberta
                     Agriculture Food and Rural Development) Provincial Horse Specialist,
                     “The horse is not able to throw up because the cardiac sphincter
                     connecting the esophagus and stomach is so strong, that food is only
                     allowed to go in one direction: Down! The horse is adapted to eating
                     small frequent meals, and therefore the sphincters work to keep the feed
                     moving constantly along the digestive tract.”




                                   cardiac sphincter




                                         pyloric sphincter



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                                                                               Causes.of.gastric.upsets.in.horses
                                                                               Conditions necessitating need to release
                                                                               of stomach contents:
                                                                               •	 Colic (abdominal discomfort)
                                                                               •	 Small intestinal tumors and
                                                                                   impactions
                                                                               •	 Refusal of food
                                                                               •	 General colic symptoms (abdominal
                                                                                   pain, turning head toward stomach,
                                                                                   kicking, laying down)




     It seems the horse is at an advantage because it cannot throw up.
First, the stomach of the equine species is very acidic like any other
species. Second, this action of the cardiac sphincter and the pyloric         “The only problem is that the
sphincter at the exiting end of the stomach allow for the continual           horse cannot vomit and therefore
movement of the digestive system in the right direction, and prevent          is more sensitive to toxins and
any backups, which could be very detrimental to the horse, causing            molds that cause problems in the
conditions including colic. Horses are very instinctive and will usually      digestive tract.
avoid harmful feed that could cause them to become ill.                       Colic is usually a complication.”
     Since it is impossible for a horse to throw up, there is no way for                     Susan Novak, Ph.D.
anything to escape the stomach. As stated by Dr. Lana Bissett, from
the Edmonton Equine Veterinary Services, “Cases of horses having
spontaneous reflux is uncommon.” Based on the anatomy of the cardiac
sphincter it will rarely release and because it so strong that the stomach
lining will rupture before the sphincter gives way. This is a bad situation
for horses and after the stomach has ruptured the horse will die.
     There is something you can do for a horse once you’ve noticed that
it’s showing colicky symptoms. But the procedure must be done quickly
before the stomach lining ruptures. The procedure is known as tubing.
A trained veterinarian must be contacted to tube the horse, and should
not be attempted by the owner, because it is very easy to make a mistake.
The vet will pass a tube (stiff with a bulb on the end) nasogastrically
(through the nose) down the esophagus, and pass it through the cardiac
sphincter, as stated by Dr. Lana Bissett, “Tubing, works well as it
forces the sphincter open which releases the pressured contents, usually
gases and sometimes fluids will be released right away or after gentle
siphoning. Recovery is usually favorable (depending on the condition).”




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posted:3/24/2010
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