Effect of a direct-fed fibrolytic enzyme formulation on nutrient intake, partitioning, and excretion in early and late lactation Holstein cows.

The effect of a fibrolytic enzyme formulation on N and P intake, partitioning, and excretion was evaluated in dairy cows in early and late lactation. Twelve lactating Holstein cows (6 early lactation, 6 late lactation) were fed diets with or without the enzyme formulation in a switchback design with three, 4-wk periods. Diets for the early lactation group contained 45% forage, and late lactation diets contained 61% forage. Cows fed diets containing the enzyme formulation gained more weight than those on the control diet; this weight gain with enzyme addition was greater in early lactation cows than in late lactation cows. The main effect of enzyme treatment did not significantly affect apparent digestibility or excretion of N and P, or retention of these nutrients in body tissue. Interactions observed between the effects of group (stage of lactation) and treatment indicated differences in the nature of the milk yield and manure excretion responses to enzyme treatment between early and late lactation cows. These interactions were due to numerical increases in milk yield, feces excretion, and N excretion in early lactation cows fed diets containing the enzyme formulation compared to control, and slight decreases in these measures in late lactation cows with enzyme addition. Cows fed diets containing a direct-fed fibrolytic enzyme formulation had increased body weight gain, but the effect of addition of the enzyme formulation on milk yield and manure nutrient excretion differed for early and late lactation cows.