Soya

By Hannah Botha, MSc Equine Science, Equus Feeds

The use of soya has become a hot topic in recent years as research continues regarding its use on the human market. Of interest to horse owners, however, is how soya suits the equine diet.

What is soya used for?

As a protein

Soya is used in most manufactured horse feeds as it is a highly valuable source of protein. Horses need vegetarian sources of protein and soya is a good option. The most valuable aspect about soya as a protein source is that it provides a close match to the horse’s amino acid needs, especially the limiting amino acids, such as lysine.

As a fat

Soya is also more than just a source of protein: in some feeds, soy oil is used to provide additional energy or calories in the form of fat. Cold-pressed, unrefined soybean oil also has beneficial antioxidant effects, including stabilising blood sugar and improving metabolic balance, which makes it a useful addition to working horse diets.

As a source of fibre

It is common knowledge that forage-based diets are the best way to maintain gut health in horses, and the fibre in forage is a main source of energy for the horse. While some horses can maintain a healthy condition on fibre alone, the majority do require additional food in the form of concentrates. For this reason, it is useful to consider highly digestible fibre (or super fibre) additions to traditional feeds. Examples of these include beet pulp products and soya hulls (see HQ136 for more information on super fibres). Soya hulls are the outer layer of the soybean, which are separated during processing. Soya hulls have roughly 31% more digestible fibre than hay, which allows commercial feeds using soya to provide more fibre per kilogram of food while still ensuring adequate energy levels.

What about the potential side effects of soya?

Because of research investigating soy-related health problems in humans, many horse owners are concerned that the same may occur with horses. In order to address these concerns, Equus contacted the world’s leading researchers in equine nutrition, Kentucky Equine Research (KER), for their opinion on this matter. “Currently there is no research (that we are aware of) proving any adverse effects of soy on horses. Much of the concern stems from human research involving effects of phytoestrogens on hormones and the endocrine system when consumed in large quantities.” As an additional factor, often those involved in the research were over-consuming soy protein or were found to be truly allergic to soy products.

As horses are true herbivores, they can have completely different metabolic responses to digesting individual ingredients. “We continue to stand behind the use of soy, in reasonable amounts, within nutritionally balanced horse feeds because it is the most abundant protein source that most closely matches the amino acid profile of the horse. KER has done research involving feeds and supplements containing soy for years with no evidence of any ill effects,” says Chelsea Martin, KER.

To feed or not to feed

As with everything, moderation is key and overfeeding any ingredient has the potential for negative effects. Providing a diet high in forage with minimal, well-balanced concentrates is always the best way to feed. Soya has many valuable properties that are of benefit to the average horse, and at this time there is no evidence to suggest any ill effects of soya in horses.

Note: 

True food allergies in horses are extremely rare. However, some horses may be sensitive to ingredients such as soya and therefore avoiding it in these cases may be prudent.

References

  • Chelsea Martin, KER.com
  • Amy M Gill, PhD, equine nutritionist, Lexington, Kentucky in an article by Lisa Kemp, 2008: www.thehorse.com/123469/soy-safteydepends-on-the-source-nutritionists-say/