The aim of this study was to evaluate the effect of an exogenous amylase on postruminal digestion of starch in cattle. Four rumen-fistulated heifers were assigned to a 2 × 2 Latin square with 2 experimental periods lasting 23 d each with 10 d of diet adaption followed by 13 d of abomasal infusion (10 h/d) and sample collection. During the first 3 d of each infusion phase, isotonic saline solution was infused (1 L/h) for measurement of basal values in feces, followed by daily infusions of 880 g corn starch (suspension of 1 kg/10 L water) with or without amylase solution (2%; 50 mL/h). The heifers were fed 5.5 kg/d of a starch-free diet consisting of 64.9% grass hay, 33.0% dried beet pulp, 0.9% urea and 1.2% of a mineral and vitamin premix (DM basis) in 2 equal meals. Titanium dioxide (10 g/d) was ruminally administered in 2 dosages for estimation of fecal excretion. Four fecal grab samples per day were obtained during collection phase, pooled by animal and analyzed for DM, N, purine bases and volatile fatty acids (VFA). Microbial N was estimated from purine bases assuming a purine N: microbial N ratio of 0.116. Abomasal infusion of starch increased fecal excretion of VFA and microbial N (P < 0.05), which indicates an enhanced carbohydrate fermentation in the hindgut and therefore limited digestion of starch in the small intestine. Lactate excretion was increased at the second day of starch infusion (P < 0.05) but returned to basal values within 2 d, which was probably due to changes in composition of microbiota in the hindgut (e.g., increase of lactate-utilizing bacteria). This agrees with increasing proportion of butyrate in total excreted VFA (P < 0.05) as an end product of lactate utilization. The increase of lactate excretion at the second day of infusion was lower with amylase administration (P < 0.05), which indicates a possible positive effect of amylase supplementation to animals not adapted to starch digestion.