AbstractTwo experiments were conducted for determining effects of applying exogenous fibrolytic enzymes to guineagrass hay (GH) [Panicum maximum Jacq. (= Urochloa maxima (Jacq.) R. Webster)] upon chemical composition, voluntary intake (VI), digestibility of various chemical fractions, and apparent and true dry matter (DM) degradability. The enzymatic products used were PromoteNET and BiocellulaseA-20, derived from Trichoderma longibratum and Aspergillus reesei. These products contain mainly cellulase and xylanase. In the first experiment, nine mature Blackbelly x creole crossbred rams of 26.8 kg mean body weight (BW) were used in a 3 x 3 Latin Square design, with 18-d periods. Treatments consisted of untreated hay (control), hay treated with PromoteNET, and hay treated with BiocellulaseA-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 treated GH in comparison with those contents of 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). The VI of DM of hays treated with BiocellulaseA-20 and PromoteNET (1,139 and 938 g DM/d, respectively) exceeded that of the control (921 g DM/d).The VI of CP, NDF and ADF were higher for hay treated with BiocellulaseA-20 than for GH untreated or treated with PromoteNET. Rams fed enzyme-treated hay had higher (P < 0.05) DM intake as a percentage of BW when compared with those fed untreated GH (4.06% for BiocellulaseA-20 0, 3.15% for PromoteNET, and 2.86% for the control). Apparent DM digestibility increased (P < 0.05) by 5.89 and 4.24 percentage units for BiocellulaseA-20 - and PromoteNET -treated hays in comparison with that of the control (50.12%). Significant increases over the control were observed in digestibility of three 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). Digestibility of dry matter, CP and ADF did not differ (P > 0.05) between enzymatic treatments, whereas NDF digestibility was higher (P < 0.05) for GH treated with BiocellulaseA-20. In the second experiment, apparent dry matter degradability (IVDMDA) and true dry matter degradability (IVDMDT) were found to be higher (P < 0.05) for GH treated with both enzymes than for those of the control (IVDMDA by 2.75 percentage units for BiocellulaseA-20, 2.12 for PromoteNET; 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 value substantially.
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