Abstract

MHLONGO, G.; MNISI, C.M.; MLAMBO, V.  and  DLAMINI, B.. An exogenous fibrolytic enzyme mixture enhances in vitro ruminai degradability of red grape pomace by-product. S. Afr. j. anim. sci. [online]. 2022, vol.52, n.2, pp.126-133. ISSN 2221-4062.  http://dx.doi.org/10.4314/sajas.v52i2.1.

Usefulness of red grape pomace (GP) by-product in ruminant rations is restricted by its high fibre content. Pre-treatment with exogenous carbohydrases may partly resolve this problem. Therefore, the effects of various levels of an exogenous fibrolytic enzyme mixture (Viscozyme^® L) on chemical nutrient content and in vitro ruminal fermentation of GP were studied. This product, with an enzyme activity of >100 fungal beta-glucanase per gram (FBG/g) and a density of 1.2 g/mL, was applied to GP at 0 (ENZ0), 20 (ENZ20), 30 (ENZ30), 35 (ENZ35), and 45 g/kg DM (ENZ45). Neutral detergent fibre (NDF), acid detergent fibre (ADF) and insoluble condensed tannins (ICT) declined linearly as enzyme levels increased. Significant negative linear trends were observed for the rate of gas production at 36 and 48 hours, whereas quadratic trends were observed at 12- and 24-hours incubation in response to enzyme levels. Cumulative gas production at 12 hours and 24 hours and in vitro organic matter degradability at 96 hours post incubation increased linearly as treatment levels increased. Effective gas production declined linearly (P =0.041; R² =0.085), whereas the slowly degradable fraction (P =0.042, R² =0.084), the fractional degradation rate (P =0.003, R² =0.175) and potential gas production (P =0.043, R² =0.083) showed quadratic trends as enzyme levels increased. Pre-treatment with Viscozyme reduced the fibre levels of GP and increased in vitro ruminal organic matter degradability. The optimum level for inclusion of Viscozyme was 5 g/kg.

Keywords : agricultural by-product; enzymes; fibre; fermentation; proximate constituents.

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