In vitro screening of Algerian steppe browse plants for digestibility, rumen fermentation profile and methane mitigation

The aim of this study was to screen the nutritive value and the effects of anti-nutritional secondary compounds (condensed tannins) on in vitro rumen fermentation and methane mitigation of Algerian steppe browse species: Albizia julibrissin (pods), Acacia nilotica (pods), Punica granatum (leaves and pericarp), Vicia faba (leaves), Artemisia herba-alba (aerial part), Attriplex halimus (leaves) and Calligonum azel (bark). Chemical composition, and in vitro digestibility, and rumen fermentation kinetics and end-products accumulation in batch cultures were determined. Polyethylene glycol (PEG), a tannin binding agent was used to measure the biological activity of tannins. Protein content was high for A. julibrissin and V. faba and low for the pericarp of P. granatum and bark of C. azel. The highest concentrations of total extractable phenols and tannins were observed in P. granatum, whereas A. halimus showed the lowest concentrations. A. nilotica, C. azel and A. julibrissin showed the highest and A. halimus and A. herba-alba the lowest total condensed tannin contents. Vicia faba was the most digestible forage. All the browse species used in the current study, with the exception of C. azel bark, can be used as alternative feedstuffs for ruminant nutrition. The most promising forage in terms of reduced methane emissions is Atriplex halimus foliage, because the decreased methane production is not associated to a reduced rumen degradation and fermentation of this forage in the rumen. However, in vivo studies are warranted to confirm its potential to be included in ruminant diets.