Effect of fibrolytic enzyme on lactational performance, feeding behavior and digestibility in lactating dairy cows fed a whole plant faba bean silage-based diet

Abstract

Faba beans (Vicia faba L.) is one of the most widespread and oldest grain legumes in the temperate regions due to its considerable content of protein and starch. The exogenous fibrolytic enzyme for ruminants was applied in order to improve feed efficiency and animal performance. The aim of this project was to evaluate the effects of pre-treating whole plant faba bean silage based- diet with exogenous fibrolytic enzyme in lactational dairy cows and develop an efficiently feeding strategy of whole plant faba bean silage for dairy cows. Statistical analyses were performed using PROC MIXED of SAS 9.4 with significance declared at P< 0.05. Orthogonal polynomial contrast was used to detect linear, quadratic and cubic effect when increased enzyme dosage to treat whole plant faba bean silage. The results obtained from in situ method show that fibrolytic enzyme cubically (P<0.05) affected in situ DMD and quadratically (P=0.01) affected in situ NDFD with increasing level of enzyme application. Both in vitro DM and NDF degradability were quadratically (P<0.01) affected by the increasing dosage of enzyme. Correlation analysis between in situ assay-biological approach and in vitro DaisyII approach showed a strong correlation (R=0.98, P<0.01) on overall DMD and also a satisfactory relationship (R=0.84, P<0.01) on overall NDFD. The washable and potential degradable (W+D) fraction of NDF was linearly (P=0.05) increased by the enzyme treatments. In contrast, undegradable fraction was linearly decreased (P=0.05) with increasing dosage of enzyme. The Kd of NDF in whole plan faba bean silage was cubically (P<0.05) affected by the enzyme. Both rumen bypass (B) and effective degradable (ED) NDF were cubically (P=0.05) affected by fibrolytic enzyme. The response of NDF digestibility and digestible NDF to the increasing level of FETR was linear (P<0.05), where lower enzyme group (0.5 mL of enzyme/kg of TMR DM) exhibited the highest NDF digestibility (48.54%). The enzyme application effects on percentage of milk fat and milk fat yield were linearly (P<0.05) affected by enzyme treatment, with the highest (4.35%, 1.82 kg/d) in low dosage group. The control milk averaged 41.2 kg/d with 4.35 percent fat. Both energy (ECM, P = 0.018<0.05) and fat corrected milk yield (FCM, P=0.058<0.10) were linearly affected or tended to be affected by fibrolytic enezyme dose level. The ECM and FCM production efficiency (kg of ECM or FCM/kg of DMI) cubically (P<0.05) and linearly affected by the enzyme application. Based on the results, it was suggested that the low dosage of enzyme for whole plant faba bean silage at 0.50 mL of enzyme/kg of silage DM has the potential to enhance substrate fermentation thus provides additional energy for animals and improve animal performance.