Dietary Enzymes Help Horses Use Feeds Better

Consumption of supplemental digestive enzymes helps horses break down fiber found in forages and improves feed intake and digestibility, according to a new study*.

Researchers conducted the study to help find new feeding strategies in horses because many forages have a low protein content and negligible nutrient digestibility.

“If we can help horses obtain the most nutrients from forage through increased digestibility, it will be healthier for horses and more economical for owners to feed them,” explained Kathleen Crandell, Ph.D., Kentucky Equine Research nutritionist.

In the study, 16 mares were divided into groups and fed one of four diets: (1) a control diet with no enzymes added; (2) the control diet plus the enzyme xylanase; (3) the control diet plus the enzyme cellulase; and (4) the control diet plus both xylanase and cellulase. The enzymes were sprayed onto a portion of the concentrate feed mix and fed twice daily with ad libitum oat straw.

Xylanase and cellulase are both involved in the breakdown of fibrous plant parts that are normally fermented in the hindgut of horses. The enzymes have been found to improve digestibility of highly fibrous forage in cattle.

Key findings of the study were:

• Forage intake increased with enzyme treatment;
• The three diets supplemented with the enzymes significantly increased total nutrient digestibility compared to the control diet;
• Protein levels in the blood were significantly higher in supplemented horses; and
• Some enzyme-supplemented horses also had decreased gas production (methane gas, which can cause colic).

The study authors therefore recommended the addition of cellulase, xylanase, or a combination thereof (in a ratio of 1:1) to achieve a maximum of 10 mL/horse/day to improve intake and increase digestibility of highly fibrous forage.

“This supplementation strategy could be particularly beneficial for hard keepers and for putting weight on skinny horses,” concluded Crandell.

*Salem , A.Z.M., M.M.Y. Eighandour, A.E. Kholif, et al. 2015. The effect of feeding horses a high fiber diet with or without exogenous fibrolytic enzymes supplementation on nutrient digestion, blood chemistry, fecal coliform count, and in vitro fecal fermentation. Journal of Equine Veterinary Science. 35:735-743.