Limits of exogenous fibrolytic enzymes to improve digestion and intake of a tropical grass

Abstract

The effect of the addition of exogenous fibrolytic enzymes (mainly xylanase and cellulase activities, 15 ml/15 kg of fresh forage), on intake, total tract digestibility and nylon bag degradability of a chopped fresh Digitaria decumbens grass was studied at 2 stages of regrowth (21 and 56-day old grasses). Moreover, comparisons between ground and chopped grass were done using the nylon bag degradability method. DM intake (g/kg BW0.75) and organic matter total tract digestibility for control and enzyme treatments respectively were 69.1 vs. 65.9 (p>0.05) and 0.723 vs. 0.727 (p>0.05) with the 21-day old regrowth. Based on the same parameters, values for the 56-day old grass were 58.1 vs. 52.7 (p>0.05) and 0.621 vs. 0.591 (p>0.05). Nylon bag degradation at 24 h of the dry matter for control versus enzyme treatments were 0.653 vs. 0.70 (p<0.05) and 0.644 vs. 0.733 (p<0.0001) for the 21-day old chopped and ground forage respectively, whereas with the 56-day old grass, corresponding values were 0.321 vs. 0.392 (p<0.0001) and 0.463 vs. 0.481 (p>0.05). The positive impact of exogenous fibrolytic enzymes (EFE) on degradability of the young and ground pangola grass may suggest that in some cases, enzyme accessibility to potentially digestible cell wall is a limiting factor in their digestion.