| Two experiments were conducted to determine the effect of application of exogenous fibrolytic enzymes on chemical composition, voluntary feed intake (VFI), nutrient digestibility, apparent and true in vitro dry matter (DM) degradability of guineagrass hay (GH) ( Panicum Maximum Jacq.). The enzymatic products used were Promote NET (Agribrand, Canada) and BiocellulaseA-20 (Loders Croklaan, Channahon, IL, USA), derived from Trichoderma longibratum and Aspergillus reesei, and containing mainly cellulase and xylanase. In the first experiment, nine (9) mature Blackbelly x criollo cross rams of 26.8 Kg mean body weight (BW) were used in a 3x3 Latin Square design, with 18 d periods. Treatments consisted of untreated hay (control), hay treated with PromoteNET and hay treated with Biocellulase A-20, applied by spraying 24 h prior to feeding. Daily hay offerings were at 4% of BW on a dry matter (DM) basis. Enzyme treatment increased contents of DM and crude protein (CP) in the GH relative to the untreated hay. A tendency to reduce neutral detergent fiber (NDF), acid detergent fiber (ADF) and hemicellulose concentrations through the enzymatic treatments was also observed, but was not significant (P<0.05). Voluntary intake (VI) of DM of hays treated with BiocellulaseA-20 and PromoteNET (1139 and 938 g/d, respectively) exceeded that of the control (921 g/d). VI of CP, NDF and ADF were higher for hay treated with BiocellulaseA-20, than for untreated GH or hay treated with PromoteNET. Rams fed fortified hay had higher (P<0.05) DM intake as percentage of BW when compared to rams fed untreated GH (4.06 BiocellulaseA-20, 3.15 Promote NET and 2.86% control). Daily DM intake as a percentage of BW was higher (P<0.05) for rams fed GH treated with both enzymatic products than for the control (4.06%, BiocellulaseA-20; 3.15%, Promote NET vs. 2.86%). Apparent DM digestibility increased (P<0.05) by 5.89 and 4.24 percentage points for BiocellulaseA-20 and Promote NET treated hays relative to the control (50.12%). Significant increases over the control were observed in digestibility of the other fractions for GH treated with BiocellulaseA-20 and PromoteNET (CP, 3.23 and 3.18; NDF, 7.96 and 4.31; ADF, 7.69 and 7.9 percentage units). DM, CP and ADF digestibilities did not differ (P>0.05) between enzymatic treatments, while NDF digestibility was higher (P<0.05) for GH treated with Biocellulase A-20. In the second experiment, apparent in vitro dry matter degradability (IVDMDA) and true in vitro dry matter degradability (IVDMDT) were found to be higher (P<0.05) for GH treated with both enzymes relative to the control (IVDMDA by 2.75 percentage units for BiocellulaseA-20, 2.12 for Promote NET; IVDMDT by 2.42 and 1.73 units, respectively). These results indicate that application of fibrolytic enzymatic complexes to low-quality tropical grass hay can improve the nutritional quality substantially. |
