Examination of the use of exogenous α-amylase and amyloglucosidase to enhance starch digestion in the small intestine of the horse

Complete digestion of starch in the equine small intestine is vital for the prevention of hindgut acidosis and laminitis. It has been proposed that a deficiency of glycanases in the equine small intestine limits the horse’s ability to digest starch pre-caecally. A trial was designed to evaluate the effect of the addition of exogenous glycanases to equine diets, on starch digestion in the small intestine. Four groups of three horses were allocated to experimental diets as follows: Group A—1.12 kg steam-rolled triticale (control); Group B—control plus α-amylase; Group C—control plus amyloglucosidase (AMG); Group D—control plus α-amylase and AMG. The glycaemic and insulin responses were measured following consumption of the grain on the 3rd (period 1) and 6th (period 2) days and were used to estimate the extent of starch digestion in the small intestine. The addition of α-amylase or a combination of α-amylase and AMG improved the digestion of starch in the equine small intestine. The addition of AMG alone had no effect. The glycaemic response to the control diet increased between periods 1 and 2 and the response to the α-amylase diet decreased, from period 1 to 2. It is concluded that exogenous glycanases may be useful for enhancing starch digestion in the small intestine and for reducing the risk of hindgut acidosis and laminitis in horses. However, further research needs to be conducted to determine whether exogenous enzymes are still needed for horses well adapted to grain based diets.