Effect of Exogenous Enzymes on Nutrient Digestibility and Ruminal Fermentation of Holstein Cows

This study aimed to evaluate the effect of different exogenous enzymes or their combination on nutrient digestibility and ruminal fermentation of Holstein cows. Five ruminally cannulated adult Holstein cows were distributed in a 5 × 5 Latin square design and received the same basal diet consisting of 30% of corn silage and 70% of concentrate but with inclusion of different exogenous enzymes comprising five treatments (control: diet without enzymes; amylase: basal diet with 7.5 g of amylase/cow/day; xylanase: basal diet with 15 g of xylanase/cow/day; cellulase + protease: basal diet with 7.5 g cellulase + protease/cow/day; and enzyme pool: basal diet with 30 g enzyme mixture (7.5 g of amylase, 15 g of xylanase and 7.5 g of cellulase + protease)/cow/day). Accordingly, the experiment was conducted in five periods of 23 days each. Therefore, data were collected to evaluate nutrient digestibility and ruminal fermentation parameters. The different exogenous enzymes or their combination (enzyme pool) did not affect (P 0.05) nutrient digestibility, ruminal pH, protozoa population, ammonia nitrogen and methane concentration and production. The enzyme combination and cellulase + protease increased (P 0.05) the concentration and production of acetate and propionate as well as total short-chain fatty acids, but did not significantly affect the relative energy loss of methane concering the other rumen fermentation products (acetate, propionate, and butyrate). Therefore, the dietary supplementation of different exogenous enzymes or their combination in Holstein cows did not improve feed value, but the enzyme combination has shown a tendency to reduce the relative energy loss of methane.