Effect of Treatment with Fibrolytic Enzymes or Ammonia on the Nutritive Value of Guineagrass (Panicun maximum) Hay^#

This study evaluated the effect of applying four fibrolytic enzymes or NH3 on the nutritive value of 6- (6-wk) and 8-week (8-wk) regrowths of guineagrass (Panicum maximum) hay. The NH3 was applied at 4% DM and enzymes Promote (Pr), Biocellulase X-20 (X-20), Fibrozyme (Fib) and Biocellulase A-20 (A-20) were applied at 0, 0.5x, 1x and 2x manufacturer-recommended rates to 2 kg of guineagrass hay in triplicate. Hays were stored for 3-weeks before determination of chemical composition and 6 and 48 h in vitro digestibility of DM (IVDMD), NDF (IVNDFD), and ADF (IVADFD). Crude protein concentration, 6 and 48 h IVDMD, and 48 h IVNDFD and IVADFD values were greater (P<0.01), while ADF and NDF concentrations were lower (P<0.01) in 6-wk hays compared to 8-wk hays. Additive treatment did not affect ADF or NDF concentration of 6-wk hays, but in 8-wk hays, X20 and Fib treatment reduced NDF and ADF concentrations (additive x maturity interaction, P<0.1). Ammoniation increased (P<0.01) CP concentration of 6 and 8-wk hays by 42 and 91%, respectively (additive x maturity interaction, P<0.01). Ammoniation increased (P<0.01) 6 h IVDMD by 35% and increased (P<0.01) 48 h IVDMD and IVNDFD by 10%, and there were no maturity x additive interactions for these measures. Additive treatment did not increase 48 h IVADFD. This study shows that guineagrass quality decreases as the duration between harvests increases. Certain enzymes produced small (<4%) decreases in the fiber concentration of 8-wk hays, but enzymes had no other effects on nutritive value. Ammoniation increased CP concentration and in vitro DM and NDF digestibility, therefore ammoniation was the only treatment that increased the nutritive value of guineagrass hays.