Abstract:
Forages play an important role in ruminant animal production worldwide. Unlocking the nutritional
potential of poor-quality tropical forages with fibrolytic enzymes would improve forage digestibility and
utilization. Using in vitro and in vivo methods this study investigated the effect of pre-treating Smutsfinger hay
for 24 hours with a mixture of fibrolytic enzyme (100% cellulase; 75% cellulase: 25% xylanase; 50%
cellulase: 50% xylanase; 25% cellulase: 75% xylanase; 100% xylanase and a control with no enzyme) on
ruminal fermentation and digestibility of nutrients by sheep. For in vitro fermentation, dry matter, neutral
detergent fibre (NDF) degradability and volatile fatty acids (VFA) were determined with standard procedures.
The same treatments were used for an in vivo digestibility trial using Merino sheep in a 6 x 6 Latin square
design. Feed intake and total tract digestibility were recorded. Rumen fluid samples were collected daily,
preserved, and analysed for VFA. The addition of 100% cellulase enzyme to Smutsfinger hay in vitro
increased (P <0.05) NDF degradability and gas production compared with the control and inclusion of 100%
xylanase enzyme. Both 100% cellulase and xylanase enzymes significantly reduced in vitro end time
fermentation pH. A 50:50 mixture of cellulase and xylanase plus enzyme in vivo, increased acetate, total
VFA concentration, and higher NDF and ADF digestibility of the test feed compared with the control.
Inclusion of a 50-75% mixture of cellulase and 50-25% xylanase enzymes treatment led to higher gas
production and butyrate concentration, decreased ruminal pH and improved nutrient digestibility
