The Thin Horse

The Abnormally Thin Horse: Causes of Weight Loss

Lately, we have seen a lot of horses that have lost weight and are underweight.  Abnormal weight loss is a condition that many horse owners have had to deal with at some time or another.  These horses may be suffering from a number of causes, but there are three common causes of weight loss in horses: malnutrition, parasitism, and dental disease. 

If a horse is underweight due to malnourishment, it is because they are not getting enough calories required for that particular horse.  A few causes of malnutrition are poor quality feed, being underfed, and competition with other horses during feeding.  Every horse requires a different amount of food.  A very active, nursing, or pregnant horse will require more caloric intake than a pasture or lightly ridden horse because they are expending greater amounts of calories per day.  If your thin horse is among other horses that are ideal weight or heavy, then you may have to separate them during feeding to see if the other horses are just eating more than them.

The next common cause of weight loss is internal parasites.  Parasites consume nutrients and cause poor absorption of nutrients because of the inflammation they cause in the horse’s gastrointestinal tract.  All horses get parasites and it is very important that they be on a parasite management program, which involves the use of appropriate dewormers given at the correct dosage.  If your horse is not on a daily dewormer, like Strongid C, then it should be dewormed every 8weeks alternating between an ivermectin-based dewormer and either afenbendazole-based or pyrantel-based dewormer.  Once to twice a year, they should be dewormed for tape worms with either a praziquantal-based dewormer or daily Strongid C for 45 days. 

The last, but probably most common cause of weight loss is dental disease.  Horses have teeth unlike people, in that they are constantly growing.  And they chew in an elliptical motion.  Both of these things can cause their teeth to develop sharp points on the inside and outsides of their teeth, which lead to ulcers of the cheeks and tongue. They can also abnormally wear the molars, which alters the way they chew their food.  You may even notice your horse dropping feed due to this. Ultimately, this decreases how efficiently a horse converts its food to energy, leading to weight loss.  In severe cases, loose, fractured, or infected teeth can cause a horse to stop eating all together.  In order to prevent dental disease or slow down the process, we “float” their teeth, taking the sharp points off of the molars and making sure everything is aligned correctly.  This should be done annually.  In some cases, usually horses older than 20, it has to be done every 6 months.  Only a licensed veterinarian can legally perform dentals on horses. And it is important to have one with experience and the appropriate equipment or more harm can be done than good.

There are many other causes of weight loss in the horse, but the three covered above are the most common and should always be addressed when assessing a horse for weight loss. Other causes of weight loss can include but are not limited to: disease of major organs such as the kidneys or liver,endocrine diseases, inflammation of the intestine, chronic infection, stomach ulcers, and cancer.  If the three common causes of weight loss have been ruled out, treated, or other abnormalities are noted from physical examination or history,  the next step is usually bloodwork and other diagnostics.

A useful tool in evaluating and reassessing weight loss in horsesis to use a body condition scoring system, which is a 1-9 scale, with 5 beingideal, 1 being emaciated, and 9 being very obese.  Ask your veterinarian for a greater description to help youproperly score your horse.  Anotherhelpful tool is the use of weight tapes. Although, bear in mind that these do not always give a very accurateweight, but at least help you see if there is weight gain or weight loss.

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