Question
My 16-hand (163-cm), 13-year-old Thoroughbred gelding is not involved in any real athletic pursuit, just an occasional trail ride. First problem: he is thin, probably a body condition score of 3, so he needs to gain weight. He is fed 2 cups of ration balancer and 2 cups of soy hull pellets twice a day, in addition to “horse hay” purchased from a local dealer, about 20 lb (9 kg). What can I do to help him gain weight? Second problem: he is becoming meaner and meaner, so I was wondering if this change in temperament could be from phytoestrogens in soy hulls. I am afraid he’s going to hurt one of us.
Answer
The forage component of your gelding’s diet seems adequate, especially if it is a good-quality grass or grass-legume hay. If there is any question that the hay you’re feeding is middling or poor quality (brown or yellow-ish brown, stemmy, weedy, unusual smell), source new hay for your horse. Forage provides much of the caloric content of any horse’s ration, so it is especially imperative for a thin horse to be offered calorie-rich hay. If possible, give your horse all-day access to forage, as this will keep his gastrointestinal tract primed.
Because you’re feeding a balancer pellet, a low-intake, low-calorie feed, you may not be providing sufficient calories to fuel weight gain. Consider changing concentrates to include a textured or pelleted feed. A performance feed that uses calorie-dense ingredients like cereal grains and fats would be appropriate for your gelding. Feeds that contain 6-12% fat provide more calories than those lower in fat.
The amount of additional feed he needs will depend on how much weight gain is needed and the type of feed or supplements you choose to feed him. For optimal vitamin and mineral nutrition, he should be fed at least the minimum recommended by the manufacturer. For a horse that needs to gain weight, you might have to feed more than minimum. Feed no more than about 5 lb (2.3 kg) in one meal.
Once you have him adapted to a new feed, you could add a fat supplement like vegetable oil (soybean or canola) or stabilized rice bran to the ration. As a general guideline, as much as 1 cup (8 oz, 240 ml) of oil or 1 lb (0.45 kg) of rice bran can be fed per meal to help boost calorie content. Some horses will prefer less or more, so there is some wiggle room with fat supplementation. The amount you are able to successfully supplement might depend too on the amount of fat in the feed.
All new feeds and supplements should be added gradually to the diet, so the gastrointestinal tract has time to acclimate to the changes. Switchovers should take a week to 10 days, or longer if the entire diet is being changed, slowly adding more feed or supplement to each meal.
Other factors that affect weight maintenance include dental health, parasite load, digestive health, and environmental conditions. These conditions frequently prevent horses from extracting optimal nutrition from their diets. Work with your veterinarian to rule out any underlying conditions for weight loss in addition to making appropriate dietary adjustments.
Using slang, your gelding may be “hangry” and expressing his displeasure through dangerous behavior. The behavioral problem you describe could be due to underfeeding or meal-feeding, e.g., when horses have access to forage for only two or three short periods a day, setting the stage for gastric ulcers and possibly hindgut acidosis. Providing a digestive buffer can help alleviate digestive discomfort and stabilize the digestive tract to promote health and function. EquiShure, a time-released buffer developed by Kentucky Equine Research, targets the hindgut to neutralize acid and improve fiber digestion and weight gain.
Regarding your specific question about phytoestrogens, which are estrogen-like compounds found in legumes such as soybeans, I do not believe your gelding’s behavioral problems are linked to soybean hulls you have been feeding him. Mare owners occasionally express concern that phytoestrogens could cause reproductive inefficiency, but behavioral changes in geldings have not been reported.
One final note on your gelding’s behavior: be cautious around your horse and seek the guidance of a professional trainer at once. Changes in his diet may help his behavior, but other issues might be causing him concern. Always respect your horse and work with him in the safest manner possible.
