Sheep feeding preference and methane mitigation potential of fodder tree leaves in the Sahelian silvopastoral zone of Senegal.

Abstract

Feed scarcity during the long dry season is a major constraint to livestock production in the Sahel. During this period, fodder trees provide a valuable source of nutrients. This study assessed sheep feeding preferences for five woody species from Senegal's silvopastoral zone (Adansonia digitata, Acacia tortilis subsp. raddiana, Balanites aegyptiaca, Guiera senegalensis, Khaya senegalensis) and evaluated their enteric methane mitigation potential. A cafeteria-style trial quantified voluntary intake, feeding time and preference coefficients of four sheep for fresh and air-dried leaves over 5 consecutive days during daily 30-min sessions. In vitro gas production assays, conducted with and without polyethylene glycol (PEG), measured total gas, methane concentration, and estimated digestibility. Leaves of A. raddiana and B. aegyptiaca showed high crude protein contents (168.7 and 167.0 g/kg DM) and metabolisable energy values (8.7 and 12.1 MJ/kg DM). In contrast, G. senegalensis and K. senegalensis contained high fibre (aNDF: 586.6 and 484.8 g/kg DM) and condensed tannins (35.8 and 66.9 g/kg DM). PEG addition increased gas production in A. raddiana, G. senegalensis and K. senegalensis, confirming tannin inhibition of fermentation. Sheep showed a clear preference (p < 0.001) for ingesting fresh A. raddiana (298 g/animal) and B. aegyptiaca (270 g/animal) leaves; feeding time and preference coefficients followed the same pattern. Preference coefficients were positively associated with crude protein and negatively linked to fibre and tannin contents, while tannin-rich species also produced less methane in vitro. Overall, A. raddiana and B. aegyptiaca emerged as valuable indigenous fodder resources for improving dry-season nutrition and potentially contributing to climate-smart livestock systems in the West African Sahel.