Comparative evaluation of chemical composition, in vitro fermentation and methane production of selected tree forages

The objective of this study was to investigate the nutritive value of leaves of six tree forage species [Acacia albida (Del.), Acacia nilotica (L.) Del., Balanites aegyptiaca (L.) Del., Leucaena leucocephala (Lam.) de Wit, Moringa stenopetala (Baker f.) Cufodontis and Morus alba (L.)] sampled from southwestern part of Ethiopian rift valley. The leaf samples were analyzed for chemical composition using official methods, and in vitro gas test was conducted to estimate their metabolizable energy content, organic matter digestibility (OMD), short-chain fatty acid (SCFA), ammonia nitrogen (NH3-N) and gas production characteristics. Crude protein was highest in L. leucocephala (213.09 g kg−1 DM) and M. stenopetala (209.80 g kg−1 DM) and the lowest was in M. alba (101.63 g kg−1 DM). The fiber (NDF, ADF and ADL) fractions were highest in B. aegyptiaca and lowest in M. stenopetala. Condensed tannin concentration ranged from 10.76 g kg−1 DM in B. aegyptiaca to 81.89 g kg−1 DM in A. nilotica. The OMD, cumulative gas volume, SCFA and NH3-N production were highest (p < 0.05) in M. stenopetala and M. alba followed by the values measured for L. leucocephala, B. aegyptiaca and A. albida and lowest was for A. nilotica. Highest methane (CH4) production per gram of dry matter was noted for M. stenopetala and the lowest for A. nilotica though opposite situation was observed when CH4 production was expressed as a ratio to total gas produced. Overall, most of the studied browse plants are desirable candidate species for mitigation of enteric methane emission while supplying optimum level of nitrogen if used as a supplement to low-quality forages.