Nutritive evaluation of foliage from some Acacia trees characteristic of Algerian arid and semi-arid areas

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Abstract. Chemical composition and digestibility of foliage from five Acacia species (Acacia nilotica, Acacia horrida, Acacia saligna, Acacia albida and Albizia julibrissin) from arid and semi-arid areas of Algeria were evaluated. Feed components of proximate analysis were determined, whereas phenolic and tannin compounds were analysed by colorimetric procedures and their activity tested using a biological assay. Digestibility was assessed by conventional gravimetric in vitro and in situ methods, and rumen fermentation kinetics were measured using the in vitro gas production technique. Results showed that all browses contained high levels of CP (157-252 g/kg DM). The content of neutral detergent fiber was highest in A. horrida (551 g/kg DM) and lowest in A. nilotica (290 g/kg DM). The content of lignin was highest in A. saligna (147 g/kg DM). The tannin concentrations varied considerably between species, but in general the plants investigated in this study had high tannin contents. A. nilotica had the highest levels of TP and TET (213 and 205 g/kg DM, respectively). The TCT content ranged from 60 g/kg DM in A. albida to 726 g/ kg DM in A. nilotica. The leguminous fodder tree A. julibrissin shows high protein content and its foliage is highly digestible probably due to its low tannin content. It was concluded that foliage from Acacia species is a protein-rich fodder for ruminants, although the high lignin and tannin content of some species represents an important constraint that could limit digestive utilization in the gastro-intestinal tract of these species.