The objective was to examine the efficacy of 8 amylases at increasing in vitro dry matter digestibility (IVDMD), ruminal fluid pH, ammonia-nitrogen (NH₃-N) and volatile fatty acids (VFA) concentration resulting from fermentation of dent corn (DC; 4-mm, ground; 0.5 g per F57 ANKOM bag). The 8 amylases (5Trga, 15C3281, 22Amylex, 23LAT, 27TrGA, 29PZ, 35C4687, 36C8955) differed in activity and were applied at doses of 0 (Control; CON) 0.25, 0.50, and 1.0 mg/g DM of DC and compared with a positive (Flaked corn; FC) and negative (Flint corn) control. Three ruminally-cannulated lactating dairy cows were used as rumen fluid donors and the substrate was in buffered ruminal fluid at 39°C in quadruplicate in 3 independent runs. Gas production was measured at 2, 5, and 7 h, while IVDMD and pH were measured at 7 h of incubation. Data were analyzed using the GLIMMIX procedure of SAS and differences were considered significant at P ≤ 0.05. Treatments and sampling time (for gas production) were used as fixed effects while run was considered a random factor. Enzymes 22Amylex and 36C8955 increased IVDMD relative to CON regardless of the dose used. However, 5Trga, 27TrGA and 23LAT increased IVDMD at the 1.0 mg/g DM dose, while 29PZ did at doses of 0.50 and 1.0 mg/g DM. Only 22Amylex increased IVDMD relative to FC at the 0.50 and 1.0 mg/g DM doses. Also, 22Amylex increased gas production at the 1.0 mg/g DM dose after 5 and 7 h of incubation, and decreased molar proportion of acetate at the 0.50 and 1.0 mg/g DM doses, relative to CON. The molar proportion of butyrate was greater with 5Trga and 22Amylex at 0.50 and 1.0 mg/g DM doses, respectively, while isobutyrate was greater for 5Trga, 23LAT, and 27TrGA at the 1.0, 0.50, and 0.25 mg/g DM doses, respectively, compared with CON. No treatment differences were observed for concentrations of NH₃-N, total VFA, propionate and acetate:propionate ratio. Amylases 22Amylex, 36C8955, 29PZ, 5Trga, 27TrGA and 23LAT increased IVDMD and their efficacy should be validated with in vivo studies.