Soy is a common ingredient in many equine feeds. Different parts of the soybean can be used to provide protein, energy, and fiber in your horse’s diet.

Soybeans are popular because of their versatility and affordability. Soy oil is a palatable fat source for horses who require additional calories.

Soybean meal and roasted soybeans also have a superior amino acid profile compared to other commonly fed protein sources. This makes soy a desirable addition to the high-protein diets required by lactating and growing horses.

However, there is a concern in the horse community about whether soy products are harmful. If you are concerned about your horse’s soy consumption, read on to learn more.

Soy Products in the Equine Diet

Soy can show up in your horse’s diet in many forms, including soybean meal, soy oil, and soy hulls.

These different forms vary in their nutritional profile and can be used to balance your feeding program based on your horse’s individual needs, including:

  • Physiological status of your horse
  • Forage quality
  • Composition of the rest of their diet
  • Health concerns

An equine nutritionist can help you determine if soy products would be suitable for your horse and how much to add to their diet.

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Roasted Soybeans

Roasted soybeans are whole soybeans that are roasted to enhance their digestibility. This means the horse can absorb and use more of the nutrients in the soybean.

Roasting destroys endogenous trypsin inhibitors, which are anti-nutritional factors that can inhibit protein digestion. [1]

This form of soy is a great source of protein and fat. Feeding roasted soybeans is beneficial in diets where extra protein and energy are needed, such as for growing or lactating horses.

Soybean Meal

Soybean meal is a dense source of protein, and a particularly good source of the limiting amino acid Lysine.

Low protein or lysine intake can lead to several issues including loss of muscle mass, weak hooves, poor growth and poor performance.

Soybean meal is a by-product of soy oil production in which the oil is extracted, leaving the protein-rich meal.

Soybean meal is added to many commercial feeds, but can also be added to the diet as a concentrate to provide extra protein. It is well digested in the horses’ foregut. [2]

Compared to alfalfa, soybean meal is just as effective for supporting growth in yearling horses and results in better protein utilization. [3]

Nutritionists often recommend soybean meal for growing or lactating horses with high protein requirements. When weighing the use of soybean meal against other sources of protein, we consider some key nutrients:

Protein:

Soybean meal typically has a crude protein content of around 44 – 48%. This exceeds other protein sources including:

  • Alfalfa (17 – 25% crude protein)
  • Canola meal (36 – 41% crude protein)
  • Ground flax (26% crude protein)

The high concentration of protein makes it a good choice for horses with elevated protein needs, but limited feed intake such as in young, growing horses.

Calcium and Phosphorus:

Soybean meal has relatively low calcium to phosphorus ratio (approximately 0.45 : 1). This makes it a good choice to balance diets that contain alfalfa for growing horses.

Alfalfa is an energy and protein-rich forage with a calcium to phosphorous ratio of 5 : 1.

Feeding a diet that provides an optimal calcium to phosphorus ratio is extremely important for development in growing horses. Soybean meal balances the high levels of calcium in alfalfa to provide growing horses with a healthy ratio of these minerals.

Soy Oil

Soybean oil is a dense source of calories for horses that need more energy in their diets.

Soy