Question

I would like some information on the digestibility of basic grains in horses and the importance of this. I give a commercial feed and add steam-rolled barley to my broodmare feed when mares have foals at foot, but I wonder if this is the best grain to use.

Answer

The basic grains fed to horses in the United States and Australia are barley, oats, and corn. Oats are by far the most commonly fed as a straight grain, while corn is probably the most commonly used in commercial feeds.  These grains are excellent energy sources but offer little more in the way of other nutrients. Some averages on digestible energy for the three grains are corn = 3.87 Mcal/kg, barley = 3.65 Mcal/kg, and oats = 3.34 Mcal/kg. (Averages obtained from Equi-Analytical.com.)

Corn is the most energy-dense of these grains because it has the most starch, which is a concentrated energy source for the horse: corn = 70.2% starch, barley = 54.9% starch, and oats = 44.4% starch. The starch found in oats is easily digested by the enzymes found in the small intestine of the horse but that is not the case for the type of starch found in corn and barley.  Both of these grains benefit from steam-flaking or steam-rolling to improve starch digestibility in the small intestine.

More of the energy in oats is derived from digestion of fiber than in either corn or barley, which can be seen by looking at NDF (neutral detergent fiber) for these grains: corn = 9.9% NDF, barley = 19.2% NDF, and oats = 27.1% NDF. If you want to add calories to the diet of the horse, any of the three grains will work, and steam-rolled barley is fine if you are happy with its palatability.

Here are a few suggestions if you are topping off a commercial feed with any of the basic grains: (1) the commercial grain should be fed to at least the minimum recommended feeding rate in order to supply your broodmare with the extra protein, vitamins, and minerals needed to support her maintenance and milk production, and to foster healthy growth of foal; (2) extra grain will supply additional calories but can upset the calcium-phosphorus balance of the diet if overfed; however, if you are feeding any alfalfa (high in calcium) this may not be of concern; and (3) forage should be the basis of the diet and too much starch from grain can interfere with proper forage digestion in the hindgut, so it is important to keep at least 50% of the diet as forage.