Chemical composition, phenolic concentration and in vitro gas production characteristics of selected acacia fruits and leaves

The objective of this study was to evaluate the nutritive value of selected fruits (pods and seeds) and leaves of acacia tree species namely; Acacia nubica (nubica), Acacia tortilis (tortilis) and Acacia brevispica (brevispica), Acacia reficiens (reficiens) and Acacia senegal (senegal). A wide variability in chemical composition, polyphenolics and gas production was recorded. The crude protein (CP) ranged from 131 to 238 g/kg DM. Neutral detergent fiber (NDF), acid detergent fiber (BDF) and lignin (ADL) were higher in senegal and significantly different (p<0.05) from other species. The nitrogen bound to fiber tended to be higher in leaves than the fruits, ranging from 2.6 to 11.3 g/kg NDF and 1.6 to 3.2 g/kg ADF. The leaves of reficiens and senegal had higher concentrations of total extractable phenolics (TEPH), total extractable tannins (TET) and total condensed tannins (TCT), but lower in NDF, ADF and ADL than the fruits of nubica, tortilis and brevispica. Mineral concentrations varied among species; all were relatively poor in phosphorus, moderate in calcium and magnesium, and rich in microelements. A significant (p<0.05) variation in gas production after 12, 24, 48, 72 and 96 h was recorded between species. Nubica had the highest (p<0.05) rate of gas production (0.0925) while the highest potential gas production was recorded in tortilis. A strong negative correlation between TEPH and TET with gas production after 24, 48, 72 and 96 was established (r=-0.72 to -0.82). Crude protein and TCT correlated negatively but also weakly with gas production characteristics. Organic matter digestibility calculated from gas production after 48 h (OMD48) ranged between 465 g/kg DM in reficiens and 611 g/kg DM in tortilis. The results of this study indicate that acacia species have the potential to be used as feed supplements.