Fibrolytic Enzymes on in Vitro Gas Production and Degradability of Tifton Hay (Cynodon spp).

Brazil’s ruminant production system is dependent on grazing native and cultivated grass pastures. Use of exogenous fibrolytic enzymes has shown promise in increasing forage utilization and also positive impacts on improving nutrient utilization in the rumen. Therefore, the aim of present study was to examine the dose effect of cellulase treated substrate (CTS), xylanase treated substrate (XTS) and equal mixed enzymes treated substrate (METS) on in vitro gas production and degradability of Tifton hay substrate. Two commercial fibrolytic enzymes, cellulase and xylanase, were tested at different dose (0, 2, 20 and 200) enzymatic units per 500 mg DM substrate, respectively. It used the semi-automatic in vitro gas production technique and six adult rumen-cannulated Santa Inês sheep served as inoculum donors. For each inoculum, blank flasks (without substrate, containing only inoculum and medium) were included in duplicate for correction of gas production and degradability data. Gas pressure was measured for determining the gas production (GP). After 24 hours of incubation, the fermentation was interrupted and rumen degradability was determined. The data were subjected to analysis of variance (ANOVA) using GLM. Tifton hay were similar and showed no effect among the treatments (P>0.05), thus mean of substrate were used. Truly degraded organic matter (TDOM) and truly degraded neutral detergent fiber (DNDF) was not affected by CTS addition (P>0.10), however total gas production (mL/g/DM), methane production (mL/g/OMD) and PF had highly significant effect (P<0.01) when CTS was added. In contrast, XTS addition had no effect (P>0.10) on all the evaluated variables; whereas METS had shown dose effects (P<0.05) for all variables. Improvement on DNDF (DNDFimp = (DNDFwe – DNDFwoe) x DNDFwoe-1) showed significant dose effect (P=0.04): DNDFimp = 0.026 ln(dose) + 0.059 (R2=0.426). The data suggest that 200 IU per 50 gram of Tifton hay of CTS or METS may improve efficiency of nutrient utilization in rumen.