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A meta-analysis on the effect of fibrolytic enzyme treatment of dairy cow diets
The objective of this study was to use a meta-analysis approach to summarize the results of experiments that investigated effects of exogenous fibrolytic enzymes (EFE) treatment of diets on the performance of dairy cows. The study evaluated data from 20 studies and 30 experiments. Treatments were classified based on predominant enzyme activities listed by the authors, which included: Cellulase (C) -Xylanase (X) (C-X), Amylase (A), Cellulase-Xylanase-Amylase (C-X-A), Cellulase-Glucose oxidase-Lactobacillus (C-GO-Lac), C-GO-Lac-Amylase (C-GO-Lac-A), Ferulic acid esterase (FAE), Cellulase-FAE (C-FAE), Xylanase-Endoglucanase-Exoglucanase (X-En-Ex), Endoglucanase-Xylanase (En-X), Exogenous proteolytic enzyme (EPE). Data were analyzed with an analysis of covariance model that included effects of study, the EFE type x application rate effect, and the application method (EFE application to the TMR, concentrate or forage). Data were weighted using the inverse of the variance of each study. Among EFE, A increased DMI (P = 0.029); C-X increased (P < 0.05) DMI, milk yield, lactose yield and NDFD; C-X-A increased (P < 0.05) DMI, milk protein yield, DMD, and NDFD; and En-X and EPE increased (P < 0.05) only milk protein concentration and milk lactose yield, respectively. Tendencies (P < 0.1) were detected for FAE to increase DMI, for En-X to increase feed efficiency (FCM/DMI) and for EPE to increase DMD. Therefore, C-X and En-X were the only EFE that increased milk yield and feed efficiency, respectively. A unit increase in the rates of application of C-X and En-X increased milk yield (P = 0.017) and feed efficiency (P =0.057) by 0.19 and 0.18 units, respectively. Applying EFE to the forage increased DMD (P = 0.003), whereas application to the concentrate or TMR increased milk lactose yield (P < 0.001). Effects of EFE on the performance of lactating dairy cows were equivocal and they depended on the EFE type x rate interaction and the method of application.
Keywords:
fibrolytic enzymes, cellulase, xylanase