The effects of an Aspergillus oryzae extract containing alpha-amylase activity on ruminal fermentation and milk production in lactating Holstein cows

The effects of an Aspergillus oryzae extract containing alpha-amylase activity (Amaize™, Alltech Inc., Nicholasville, KY) were examined in vivo and in vitro. A lactating cow study employed 20 intact and four ruminally fistulated Holstein cows in a replicated 4 x 4 Latin-square design to examine the effects of four concentrations of dietary Amaize™ extract on milk production and composition, ruminal fermentation and serum metabolite concentrations. The treatment diets contained 0, 240, 480 or 720 alpha-amylase dextrinizing units (DU) per kg of total mixed ration (TMR) (dry-matter basis). The supplemental alpha-amylase increased the yields of milk (P = 0.02), fat (P = 0.02) and protein (P = 0.06) quadratically. The maximum milk yield was obtained when 240 DU per kg of TMR were offered. Ruminal in situ starch disappearance was not affected by alpha-amylase supplementation in lactating cows or ruminally cannulated steers. Supplemental alpha-amylase extract reduced the molar proportion of propionate in the rumen of steers (P = 0.08) and lactating cows (P = 0.04), and in rumen-simulating cultures (P = 0.04). The supplement also increased the molar proportions of acetate (P = 0.06) and butyrate (P = 0.05), and the serum beta-hydroxybutyrate (P = 0.01) and non-esterified fatty acid (P = 0.03) concentrations in lactating cows. The improvements in milk production appear to be a consequence of the effects of alpha-amylase on ruminal fermentation and the potential changes in nutrient metabolism that result from them. We conclude that supplemental alpha-amylase may be given to modify ruminal fermentation and improve milk and component yield in lactating Holstein cattle.