You've begun noticing your horse appears to be losing weight. As a responsible horse owner, you are concerned and would like to discover the cause for the problem so that you can take steps to fix it. There are several possible causes, depending upon the time of year, the age of your horse, type of hay or feed being given, the amount of exercise your horse receives, and physical condition.
I'm going to list some of the most common causes and possible solutions to them. Remember, NOTHING takes the place of your vet coming to perform a physical examination!
Age of Horse
If your horse is 18 years or older, it's a good possibility that he's not receiving the necessary nutrients from his feed any longer.
Solution
Try switching him to one of the widely available special feeds for senior horses. Most are complete nutrition that the older horse requires.
Condition of Teeth
Older horses may have lost teeth, others may have ground their teeth unevenly. In order to pinpoint this as the cause, you need to watch your horse eat his grain a few times. Does he hold his head strangely? Does his mouth appear to not have the teeth meeting in a proper chewing motion? Is he 'losing' a lot of his grain while eating? 'Losing' grain means a goodly amount is falling from his mouth during the chewing process.
Solutions
Have your vet or an equine dentist check your horse's teeth. A simple float may be required to even the grinding surfaces of his molars, or a more involved procedure may be required if the surfaces are extremely uneven. If your horse is older, and has lost some or many of his molars, switch him to a senior feed. Senior feeds are pelleted and begin dissolving into a paste upon contact with saliva, making them very easy for even a toothless horse to ingest.
Parasites
Intestinal parasites such as a variety of worms can cause weight loss, as they absorb the nutrients from feed that your horse needs.
Solution
Set up a regular worming schedule for your horse. I worm every three months, others worm monthly or bi-monthly, and yet others worm only once or twice a year. Experiment carefully to see what gives your horse the best results, or consult your vet.
Worming
Worming too often or at too high of a dosage.
Solutions
Double check your dosage before worming, and worm less often. If you're worming once a month, try once every two months. You may even try switching to a wormer with a different active ingredient.
Grain
Feeding large amounts of grain to a horse that isn't receiving heavy use, or changing from one brand of grain to another.
Solutions
Return to your previous brand of grain, if you've switched. You should always introduce new feeds slowly, in small amounts, until you are feeding the desired or recommended amount. Horses that aren't being worked regularly do not require large amounts of grain! Grain is harder for a horse to digest, so check his stools to see if you can spot any undigested grain in them. If you can, you're feeding too much grain, so cut the amount down.
Hay
Too much rich first or second cutting alfalfa can cause diarrhea, and therefore weight loss. Over grazing on new grass growth can also cause the same problems. Your horse not receiving enough roughage (hay) can also cause weight loss.
Solutions
Limit your horse's grazing time on new spring grass. Cut down on the amount of alfalfa fed daily, and supplement with a lower protein grass hay. Add grass hay to your horse's diet for more roughage if you're feeding less than 10lbs a day.
Sand in the Gut
If your horse eats off the ground, whether during feeding times or when grazing in the pasture, he can ingest sand or dirt, which settles in his intestines and can block the absorption of nutrients.
Solutions
Don't feed your horse on the ground. Place grain and hay in some type of hanging feeder or large container. To help clear out a gut full of sand or dirt, you can try adding bran to every other evening feeding for a few days. Bran works as a scour when moving through the intestines, and will pick up sand/dirt so that it's evacuated in your horse's manure. Your vet may recommend a different additive that will do the same thing.
