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Solving the Weight Loss Mystery


I have a 10 yr warmblood/thoroughbred. I got him last fall and he was on high fat high fibre. His weight went down so we have switched him to purina trimex which is supposed to give him all the calories he needs. He has been dewormed recently, he does not spill his feed when he eats and gets through his meals fine. I believed his teeth are good. He is on grass now and always has hay. He lives with 2 others but is used to a herd. I was thinking about checking for ulcers? Any ideas? – Amanda W. via AAEP Ask the Vet

If I were your veterinarian trying to help you figure out why your horse lost weight and how he might gain it back, I would want to know a couple more things. For example, what was his body condition score (BCS) last fall when you acquired him and what is it now? Each BCS is about 50 pounds (slightly more for a larger horse like a warmblood or draft) so if he was a 5 and is now a 4 then he lost 50-75 pounds. If he is a 3 now then he may have lost more like 100-150 pounds.

Next, where do you live and where did the horse come from? If in a northern climate, do you think he either did not acclimate to the move or just in general has a hard time keeping warm in cold weather and burns a lot of calories to do so? I had an OTTB that would consistently lose weight in the SUMMER because he didn’t tolerate the heat or bugs well and just stood around stomping instead of eating so make sure you understand your new horse’s personality and metabolism when it comes to seasonal weather changes.

What do you do with this horse? If he came from a pasture ornament situation into full training and is now expected to compete in dressage, eventing or as a hunter/jumper, then his caloric intake needs to increase accordingly.

You mention that he is used to being in a herd and now lives with two other horses. How did the establishment of pecking order go? Do you know where he is in herd hierarchy? Sometimes horses get pushed off their hay pile prematurely and spend the bulk of their eating time getting moved around, which uses up calories instead of taking them in. The warmblood I have now wears a grazing muzzle at all times because he can inhale all eight piles of hay in “his” seven-horse paddock faster than you can say “easy keeper.”

Since you also describe the grain that he eats (Purina TriMAX, available in Canada) I’m assuming you bring your horses into stalls for meals or in some way separate them so they can eat their fair share in peace? Speaking of “fair share,” Purina recommends feeding a range 0f 0.5 to 0.75kg grain per 100kg body weight. If we assume your horse weighs 500kg (1100lb) then he should be getting 2.5 to 3.75kg each day (5.5 to 8.25lb), aiming for the lower end of the range to meet his minimum vitamin, mineral, and protein needs and the higher end of the range to provide extra calories for heavy work or weight gain. Remember the rule of thumb: no more than 0.5% of a horse’s body weight per grain meal, which for a 500kg (1100lb) horse is 2.5kg (5.5lb). To use this grain as it is intended then, you should be giving your horse 1.875kg (a little over 4lb) in the morning and in the evening.

Since that’s a lot of grain and feeding large amounts of grain has been linked to gastric ulcers, you may want to provide calories via another route, such as beet pulp, alfalfa cubes, a fat supplement or other option. Each horse responds differently to these various methods of increasing the energy in the diet so I recommend trying one at a time, for about a month, before moving on to the next. The clinical signs of ulcers, their diagnosis, treatment and prevention have been covered in great detail elsewhere, so I’ll let you research those facts on your own!

Finally, if you have not had a qualified person actually examine his mouth and inspect his teeth since you purchased him (and performance horses usually get looked at twice a year) then it’s time. Also, I strongly urge you to read AAEP’s guidelines on parasite control, to make sure your program is as up-to-date as possible. If careful consideration of what changed in his life since you purchased him and attention to the details of his diet don’t improve things, then it may be time to have your vet out again to examine him and try to get to the bottom of his weight woes.

Lydia F. Gray, DVM, MA SmartPak Staff Veterinarian and Medical Director Dr. Lydia Gray has earned a Bachelor of Science in agriculture, a Doctor of Veterinary Medicine (DVM), and a Master of Arts focusing on interpersonal and organizational communication. After “retiring” from private practice, she put her experience and education to work as the American Association of Equine Practitioner’s first-ever Director of Owner Education. Dr. Gray continues to provide health and nutrition information to horse owners through her position at SmartPak, through publication in more than a dozen general and trade publications, and through presentations around the country. She is the very proud owner of a Trakehner named Newman that she actively competes with in dressage and combined driving. In addition to memberships in the USDF and USEF, Dr. Gray is also a member of the Illinois Dressage and Combined Training Association (IDCTA). She is a USDF “L” Program Graduate and is currently working on her Bronze Medal. Find Dr. Gray on Google+

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