Potential for enteric methane emissions mitigation in zebu cattle through Leucaena leucocephala and Gliricidia sepium leaf supplementation compared with cottonseed cake in West Africa

In West Africa, legume trees are widely used by agro-pastoralists to enhance livestock productivity, yet their potential to mitigate enteric methane (eCH₄) remains insufficiently documented. This study evaluated the effects of supplementing Panicum maximum hay with leaves of Leucaena leucocephala and Gliricidia sepium leaves on feed intake, apparent digestibility, and eCH₄ emissions in Sudanese Fulani zebu bulls (244 ± 24.3 kg). Animals were housed in individual stalls and received daily rations equivalent to 2.5–3.5% of body weight on a dry matter (DM) basis. The control diet consisted of 100% P. maximum C1 hay diet (P100), while experimental diets included mixtures of P. maximum with leucaena or gliricidia leaves at ratios of 90:10, 80:20, 70:30 and 60:40. Two additional diets combined P. maximum with cottonseed cake, matched for crude protein (CP) content to the 20% legumes-supplemented diets. Each trial lasted 21 days, with 14-day adaptation period and 7-day data collection (feed intake, apparent digestibility, eCH₄ emissions). Tree legume supplementation increased CP content and reduced fibre content in the rations. Compare with the control, dry matter intake rose by 11− 18% with leucaena leaves ( p <0.05) and by 4%—8% with gliricidia leaves ( p <0.05). Crude protein digestibility (CPd) increased in supplemented diets whereas organic matter, dry matter, neutral detergent fibre, and acid detergent fibre digestibility declined in supplemented diets. eCH₄ yield (g/kg DMi) decreased significantly by 12.3% with 30% leucaena and by 5% with 30% gliricidia inclusion ( p <0.05). Supplementation with cottonseed cake also significantly enhanced feed intake ( p <0.05) and produced emission reductions comparable to leucaena. These findings demonstrate that incorporating forage trees leaves or cottonseed cake into cattle rations improves ration quality, enhances intake, and reduces eCH₄ emissions. Such practices align with agroforestry initiatives, offering cost-effective protein supplementation while supporting climate-smart livestock production and enhancing local knowledge and practices in West Africa and beyond.