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Why Won't Your Skinny Horse Fatten?

Pet Column for the week of November 8, 1999

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
By Sarah Probst
Information Specialist

Americans usually don't have to worry about being too skinny. Thus, it is difficult to
understand why a horse might have trouble putting on weight, especially if food is readily
available. Horses can drop pounds for a wide variety of reasons, ranging from a simple
management problem to a malabsorption disorder that your veterinarian can help solve and

Feeding management is key. "Always consider the pecking order of horses," says Dr.
Thomas Goetz, equine veterinarian at the University of Illinois College of Veterinary
Medicine in Urbana. Dr. Goetz remembers going to check on a skinny horse with a
professor when he was a veterinary student. One of the first things they did was watch how
the horses were fed.

Two piles of hay were placed in the fenced area about 50 yards apart. Immediately a rather
plump mare rushed up and started eating from one of the piles. When the very skinny
gelding made for the other pile she ran over and chased him away. The gelding circled over
to the first pile but, before he could take a bite, the mare chased him away again. The very
hungry victim got exercise, but no feed. Feeding him separately solved that skinny horse

Check the quality of the feed. Your horse needs food equal to about 2.5 percent of its
body weight per day. Depending on its stage of growth, 9 to 18 percent of calories should
come from protein. A horse's weight can easily be maintained on grass hay, which is 11
percent protein. But a growing or hard-working horse may need alfalfa hay and/or grain.
Alfalfa hay is 15 to 20 percent protein, while grain mixes range from 9 to 12 percent
protein. Work with your veterinarian to choose the right amount of protein for your horse.

Your horse could have a dental problem. "There are two reasons to take care of horses'
teeth: for the good of the horse, and to save money," says Dr. Gordon Baker, equine
veterinarian formerly at the College and co-author of the first textbook on equine dentistry. Horses'
teeth can develop abnormalities of wear, which usually present as points or hooks of
enamel on the sides of teeth closest to the cheeks. These points can damage the mouth,
leaving your horse with pain and discomfort during chewing. Having your veterinarian float
(file) your horse's teeth regularly can prevent a dental problem that may make your horse
not want to eat. A young horse that is still teething needs a dental exam twice a year. A
yearly dental exam should be sufficient for horses kept on pasture; however, horses kept in
stables on hay and grain diets tend to have more teeth problems and should be checked
twice a year. With proper dental care, your horse will be able to grind food better and thus
better utilize nutrients, so it will need less food.

Your horse could have parasites. Devising a parasite control program for your horses
can be a confusing task, especially when recommendations advise alternating the
de-wormer used. "Rotating your de-wormer--not by brand but among classes of
drugs--can prevent parasites from developing drug resistance, thus preventing development
of a 'superworm,' " explains Dr. Doug Hutchens, veterinary parasitologist formerly with the College.
The best way to develop an effective parasite control program is to contact your local
equine veterinarian, who will know the prevalent parasites and transmission patterns in your

The food could be malabsorbed. Parasite penetration of the intestine wall, atrophy of the
villi on the intestine wall, infectious diseases, and cancer can cause food malabsorption in
horses. To diagnose your horse with this problem, your veterinarian may need to do a
carbohydrate absorption test or an intestinal biopsy. The absorption test measures how well
a specific indicator is being taken into the body via the intestines. Depending on where the
malabsorption is in the intestine, your veterinarian can change your horse's diet to optimize
energy absorption. For example, if the small intestine is the section not working well, your
veterinarian may suggest a high-roughage/low-grain diet that allows the large intestine a
better chance to absorb energy needed to put weight on that skinny hoss.

For more information, contact your local equine veterinarian.