Ask the Vet: Equine Nutrition

Answered by, Lydia Gray, DVM, MA, SmartPak Equine
Courtesy of AAEP

Question: Beet pulp (unmolassed/unsweetened) for IR horses, yes or no? I’m getting conflicting information depending on who provides the answer: beet pulp manufacturers, commercially-processed horse feed companies, or holistic/homeopathic experts. Some say the sugar content is low enough to be safe for EMS horses and others say there will always be residual sugar so it’s not recommended. Who do I trust? 

Answer: There’s a long story and a short story. The short story is that all versions of beet pulp range from 10 to 12% sugars and starches. This is at/below the level of simple carbohydrates that most experts recommend for IR horses.

The long story is that, opposite to what you might think, dried shredded beet pulp WITH ADDED MOLASSES actually has less sugars and starches than dried plain shredded beet pulp. That is, the molasses-added beet pulp averages about 10% simple carbs while the molasses free beet pulp contains more like 12% Turns out that during processing of both types of beet pulp, molasses is added back as a dust control measure but at lower levels.

To really understand the impact of beet pulp to your horse’s diet though, you must calculate out the sugars and starches into grams and not think of them in terms of percents. That’s because a horse may eat 20 pounds of a 10% total sugar/starch hay but only 1 pound of a 10% sugar/starch beet pulp. Here’s how that looks multiplied through so you can see for yourself the total amount your horse would be getting from each feedstuff:

  • 10% of 20 pounds of hay = 2 pounds or just under 1 kilogram (0.9kg or 900 grams) of sugar
  • 10% of 1 pound of beet pulp = 0.1 pound or 0.04kg which is 40 grams of sugar

Because horses get so much less beet pulp by weight, they are also getting much less sugars and starches. However, if you have a particularly sensitive individual, by all means soak the beet pulp for at least an hour (you’re probably soaking it anyway) then rinse and drain to remove even more of its sugar and starch content.

Question: I live in an area where the soil is selenium and magnesium deficient. They are fed grass hay and all receive a ration of senior feed. What would be a good source of supplements that can address the lack of selenium and magnesium What are the daily requirements I should be looking for. Horses range in age of 14 to 30. 

Answer: According to the NRC Nutrient Requirements of Horses, an 1100lb adult horse in no work needs 7.5 grams (7,500 milligrams) of the macromineral magnesium a day, with that amount doubling to 15g if the horse is in very heavy exercise. The average size mature horse needs 1mg of the micromineral selenium daily, with even very heavy exercise only modestly increasing the amount to 1.25mg.

In order to complete and balance the diet of a horse, it is important to know how much of these and other nutrients they are getting from their combined feedstuffs (hay, grain, supplements, etc). The first step is having your forage analyzed – which it sounds like you’ve already done – and the second step is totaling all the amounts to find the areas where the diet is deficient. is an online tool that can easily help you do this, especially since they already have most commercial grains and supplements in their extensive database.

The third and final step is selecting products that bridge the gaps that you’ve identified. This can be done in a variety of ways, including providing a higher amount of the commercial, fortified grain you are already using; by providing a different commercial, fortified grain; by supplementing with targeted products that provide just magnesium and just selenium, or even by having a company use your feed analysis to custom blend a product just for your horses.