Question

Timmy is my 17-year-old, 1,150-lb (520-kg) Thoroughbred school-horse gelding. He splits his time between a stall and a pasture, usually about half the day in each environment. He is ridden one to two times a day in beginner or intermediate lessons, five or six days a week. Aside from the pasture, he is given timothy hay (six flakes a day) and alfalfa hay (about one flake a day, maybe less) when he’s stalled and six lb of a high-fiber concentrate each day (split into morning and evening meals). He is also given MSM and firocoxib. Last week we observed him making noises that sound very much like hiccups in humans. The muscles in Timmy’s abdomen would contract when he would make the noise and relax otherwise. He stopped making the noise after about 10 minutes of hand-walking. Another horse, a five-year-old Thoroughbred gelding that is on a similar feeding program, was observed with the same condition a week or so later. We’re baffled. What do you think?

Answer

I do not want to replace sound advice from your veterinarian, so I was wondering if you had either of the horses examined? Veterinary consultation is an important first step whenever any health concern arises.
From what you describe, it sounds to me like the horse was experiencing a condition called “thumps” (synchronous diaphragmatic flutter or SDF). Thumps results from dehydration or dramatic fluid shifts in cells that cause the diaphragm to start contracting spasmodically. This condition is fairly common in endurance horses during a competition, but it is quite unusual to hear of it in a fit school horse. (Read a related question from a horse owner.)

Here are a few ideas:

1. Although not common in Virginia, did you notice whether there were any blister beetles in the alfalfa hay? In the United States, blister beetles are found primarily in alfalfa grown in southern and lower midwestern areas.

2. Has there been any problem with the water intake with this gelding or any of the other horses on the property? Do horses have free-choice access to water whenever they’re not in work or immediately following work? Is it possible this gelding was dehydrated?

3. You did not describe if exercise led to the episode. Was he worked immediately prior to the episode or was he exercising when it occurred? Was the temperature abnormally warm, and was the horse sweating a lot? Do the horses receive some type of electrolyte (including salt)?

4. What is the calcium content of the hay and the feed? Alfalfa is normally very high in calcium. Regular intake of high levels of calcium can predispose a horse thumps, but it would usually not show up unless the horse was working hard over extended periods of time and sweating a lot.

By systematically looking at the gelding’s nutritional management and environment, you may be able to figure out why your gelding developed thumps.