Overweight Horses: How Much Hay Is Too Little?

To some horse owners, maintaining easy keepers on an appropriate diet requires incredible restraint. While owners may wish to turn their horses out in bountiful pastures, they know it’s best to limit intake and use the drylot or grazing muzzle instead. Likewise, caretakers who want to dish out just a few pounds of sweet feed refrain from doing so and offer a balancer pellet in lieu. When it comes to hay, these same horse owners know too much is not helpful, but how much is too little?

With a limited menu available for overweight horses, maximizing hay intake is important, said Catherine Whitehouse, M.S., a nutrition advisor with Kentucky Equine Research (KER). “Hay intake should be about 2% of body weight, if horses are receiving no other feed or forage.”

If the horse requires weight loss for optimal health, less hay can be fed, about 1.5% of body weight.

“Though it doesn’t seem like a large difference, reducing hay intake to 1.5% of body weight should be considered the absolute minimum,” said Whitehouse. “Anything less than this might cause gastrointestinal problems for horses.”

A horse’s weight can be estimated through the use of a weight tape, usually available for purchase at tack shops and feed stores. Once the body weight is estimated, calculating how much hay a horse requires becomes simple. Multiply the weight of the horse times 0.02 (for 2%). A 1,200-lb (545 kg) horse requires about 24 lb (11 kg) of hay per day to maintain body weight, so long as no work is asked of it. By weighing the hay available, the appropriate amount can be determined and fed. If a horse owner calculates that one flake of hay weighs 3 lb (1.4 kg), then this 1,200-lb (545-kg) horse should receive about eight flakes of hay each day to maintain body weight (3lb [1.4 kg] x 8 flakes = 24 lb [11 kg] of hay).

“How that hay is fed to the horse is key,” continued Whitehouse. “The hay can be strategically offered to extend the time it takes for the horse to consume it. This is usually done by placing the hay in a feeder that allows only small bites, such as a haynet with tiny holes, sometimes referred to as a slow-feed haynet.”

One study* demonstrated that mature horses fed off of the stall floor consumed hay at a rate of 3.3 lb (1.5 kg) per hour, while those fed from a slow-feed haynet with 1-inch (2.54-cm) holes consumed 1.9 lb (0.86 kg) per hour. Using the example above, eight flakes of hay, or 24 lb (11 kg), would give the horse a little over seven hours of chew time. If the same horse were to eat the eight flakes from a slow-feed haynet, as described above, it would take nearly 13 hours of time. Protracted periods of eating mimic natural grazing patterns and are most healthy for horses.

If the horse is in a large barren field or drylot, hay can be placed in several stations. This will encourage horses to move, which is also important for horses on restrictive diets.

In addition to how hay is fed, consideration should be given to the type of hay offered to an overweight horse. High-quality hays typically pack more calories than those of middling quality. Overweight horses generally do not need the best hay money can buy, but they do need hay that is free of mold, dust, weeds, and other extraneous material. A mid-quality grass hay that has been properly harvested will usually work well. Hay can be analyzed to determine its nutritional value; by having this analysis available, a nutritionist can pencil out an appropriate diet for the horse.

All horses on forage-only diets should receive a well-formulated vitamin and mineral supplement, as dried forages lose much of their nutrient content as they are processed and stored. Micro-Max is a low-intake source of digestible vitamins and minerals that fulfills the nutrient requirements of horses on all–forage diets. In Australia, look for Gold Pellet, Perform, or Nutrequin to round out the diets of horses fed only forage.

*Martinson, K., E. Glunk, and W. Weber. The effect of hay net design on rate and amount of forage consumed by adult horses. University of Minnesota Extension.