Digestion, ruminal pH, salivation, and feeding behavior of lactating dairy cows fed a diet supplemented with fibrolytic enzymes

The objectives were to determine the effects of supplementing different components of the diet with enzymes on dry matter intake, ruminal fermentation, total tract digestion, milk production, and effective fiber. Eight multiparous and four primiparous lactating Holstein cows were used in a replicated 4 x 4 Latin square design to investigate the effects of supplementing a diet with a fibrolytic enzyme product containing mainly xylartase and cellulase activities. A total mixed ration (TMR), consisting of rolled barley, barley silage and alfalfa haylage (forage to concentrate ratio of 55:45, dry matter (DM) basis) differed in enzyme application: 1) no enzyme, 2) enzyme applied to concentrate (45% of TMR), 3) enzyme applied to supplement (4% of TMR), and 4) enzyme applied to premix (0.2% of TMR). Application rate was constant for enzyme treatments at lg/head/day. Digestibility of DM measured using multiparous cows increased by 12% compared to the control when enzyme was added to the concentrate. Enzyme treatments that were applied to a smaller component of the TMR did not increase digestibility compared to the control. There were no significant effects of enzyme supplementation on milk production and composition. However, cows fed concentrate supplemented with enzyme produced significantly more milk than cows receiving the enzyme applied to the premix. Enzyme supplementation did not alter daily time spent eating or ruminating, indicating that this fibrolytic enzyme product does not alter the physical structure of the feed. However, when enzymes were added to the ration daily saliva production increased, which may have been a physiological response to the increase in fermentation products due to increased digestion. Enzyme supplementation did not change the mean ruminal pH or the amount of time pH was below 5.5, which was attributed to increased saliva production. The higher DM intake of multiparous cows was manifested in a faster eating rate, and resulted in more rumination time and greater saliva secretion. These results indicate that enzyme supplementation increases digestibility, and consequently improves the energy status of the cow. The component of the diet to which the enzyme is applied must be maximized to ensure a beneficial response.Land and Food Systems, Faculty ofGraduat