Chemical composition, in vitro dry matter digestibility and in vitro gas production of five woody species browsed by Matebele goats ( Capra hircus L.) in a semi-arid savanna, Zimbabwe

Abstract

The chemical composition, in vitro dry matter digestibility (IVDMD) and in vitro gas production (IVGP) of five woody species: Commiphora pyracanthoides, Terminalia prunioides, Acacia tortilis, Faidherbia albida and Dichrostachys cinerea browsed by Matebele goats in an open semi-arid savanna was determined at three leaf phenophases. T. prunioides had the highest IVGP volume (80.1 ml) and C. pyracanthoides the highest IVDMD (0.60) with D. cinerea having both the lowest IVDMD (0.39) and IVGP volume (43.7 ml). This was presumably due to the high condensed tannins (CT) in D. cinerea (20.1 A 550 nm ) as compared to the low CT in T. prunioides (1.2 A 550 nm ) and C. pyracanthoides (2.9 A 550 nm ). T. prunioides had lower acid (240.6 vs. 354.4 g/kg DM) and neutral (351.2 vs. 430.5 g/kg DM) detergent fibre than C. pyracanthoides. Crude protein (CP) and IVDMD declined while neutral detergent fibre (NDF) and acid detergent fibre (ADF) increased with leaf maturity. In vitro dry matter digestibility was not influenced by CP ( r = 0.09, P>0.05) and NDF ( r = −0.29, P>0.05) while ADF negatively affected IVGP ( r = −0.54, P<0.05). Gas production was positively associated with IVDMD ( r = 0.54, P<0.05). Condensed tannins had a greater negative effect on IVDMD ( r = −0.58, P<0.05) and IVGP (−0.68, P<0.01) than acid ( r = −0.46, P>0.05; r = −0.54, P<0.05) and neutral ( r = −0.29, P>0.05; r = −0.51, P>0.05) detergent fibre. Total phenolics were positively correlated to IVGP ( r = 0.73, P>0.05). We conclude that T. prunioides had good rumen fermentation attributes due to low NDF, ADF and CT contents.