Effects of exogenous amylolytic enzymes on fermentation, nutritive value, and in vivo digestibility of rehydrated corn silage

This study aimed to evaluate the effects of amylolytic enzymes incorporation - into rehydrated ground corn on silage fermentative profile, chemical composition, microbiological profile, as well as their effects on feed intake and total tract apparent digestibility in lambs. Twenty-four silos of rehydrated ground corn with theoretical particle size of 2.5 mm and 625 g/kg DM content were used in a completely randomized design containing the following treatments: 1) Control (CON), without exogenous enzymes; 2) Glucoamylase (GLU), incorporation of 300 L of glucoamylase product (Kerazyme 4560-300 U/mL, Kera Nutricao Animal, Bento Goncalves, RS) per kg of ground corn (as-fed basis); and 3) alpha-amylase (AMY), incorporation of 300 mu L of alpha-amylase product (Kerazyme 4577-300 U/mL, Kera Nutricao Animal) per kg of ground corn (as fed basis). Nine castrated lambs (25.4 +/- 4.57 kg body weight and 6.0 +/- 0.4 months age) were enrolled to a 3 x 3 Latin square design to evaluate effects of silages with amylolytic enzymes on nutrient intake and total apparent digestibility. Enzyme products (GLU or AMY) increased (P <= 0.043) fermentative losses and decreased (P = 0.002) DM recovery of rehydrated corn. Silage treated with GLU tended to show greater (P <= 0.052) fermentative losses than those treated with AMY. Enzyme products increased (P < 0.001) DM content without (P > 0.135) having major effects on chemical composition of rehydrated corn. On the other hand, enzyme products increased (P = 0.003) 48 h in vitro DM degradation and amylase activity, especially in silage treated with GLU. Regarding the enzyme treatments, GLU increased (P <= 0.004) amylase activity, counts of lactic acid and aerobic bacteria, NH3-N and lactate concentrations while decreasing (P = 0.019) acetate concentration. Enzyme products decreased (P <= 0.034) pH and ethanol concentration and increased (P = 0.027) concentrations of butyric and lactic acids. Lambs fed rehydrated corn treated with enzyme products had greater (P <= 0.050) DM, CP, and starch intake and digestibility in relation to those fed CON. In addition, feeding AMY silage increased (P = 0.035) DM intake without affecting (P >= 0.713) nutrient digestibility in relation to GLU. In conclusion, there is evidence that enzyme products promote fermentation in rehydrated corn, which can further improve feed intake and nutrient digestibility in lambs. In addition, GLU treatment has a greater impact on silage fermentative losses but lambs fed GLU has lower DM intake than those fed AMY.