Enteric methane emission response to peanut (Arachis hypogaea) and cowpea (Vigna unguiculata) haulms supplementation in zebu cattle diets

Improving the quality of ruminant rations is a promising strategy for mitigating the climate impact of livestock farming in West Africa. Legume crop coproducts such as peanut ( Arachis hypogaea ) and cowpea ( Vigna unguiculata ) haulms are a high-protein fodder commonly used by agropastoral farmers during the dry season. This study evaluated their potential to reduce enteric methane (eCH 4 ) emissions when used as supplements for Panicum maximum C1 hay. Ten Sudanese Fulani zebu bulls (49 ± 1.2 months; 183.7 ± 15.9 kg) were housed individually and fed 11 diets ad libitum : a control diet of 100% P. maximum and 10 experimental diets combining P. maximum with either peanut or cowpea haulms at ratios of 85:15, 70:30, 55:45, 40:60, and 25:75. Each trial lasted 21 days, comprising a 14-day adaptation period and a 7-day data collection period for feed intake, digestibility, and eCH 4 emissions. The latter were measured six times daily using the GreenFeed system. Supplementation increased protein content by 47.5% to 183.5% and ADL by 2.6% to 48.2% while reducing the content of crude fiber, NDF, and ADF. Feed intake increased by 17.8% to 49.1% ( p < 0.05), and digestibility improved by 4.6% to 9.9% ( p < 0.05). Peanut haulms reduced eCH 4 yield by up to 6.1% ( p < 0.05), while cowpea haulms achieved reductions of 3.7%–4.8% ( p = 0.14). The most effective mitigation was achieved with 75% peanut or 45% cowpea haulms, confirming the potential of legume coproducts to enhance feed efficiency and reduce eCH 4 emissions in West African cattle systems.