Nutritional values, phytochemical profiles and enteric methane mitigation potential of West African indigenous forage species for sustainable ruminant livestock production systems

Manipulating feed rations with forages containing specific natural phytochemicals that reduce enteric methane emissions is a sustainable strategy for cattle farming. This study aimed to select forages based on their secondary metabolites, nutritional value and methane production. A total of fifteen forage species identified by cattle farmers were studied. Phytochemical parameters were measured in line with the European Pharmacopoeia method. In vitro fermentation with bovine rumen juice was used to assess digestibility and methane production. Results showed that species with high tannin content: Acacia sieberiana (2.002%), Khaya senegalensis (1.939%) and Detarium microcarpum (1.665%) had the lowest digestibility values of Organic Matter Digestibility (OMD ranging from 30.0 to 47.1%) and metabolizable energy values (1281.6 to 1952.4 kcal/kg DM). These low energy values were also coupled with low methane production (185.0 to 282 mL CH 4 /kg DM). Furthermore, despite their high tannin contents, Anogeissus leiocarpa (4.556%) and Isoberlinia doka (2.486%) recorded good digestibility, good energy values, and moderate methane production. However, species that are poor in tannins and rich in nitrogen, such as Blighia sapida , Leucaena leucocephala , and Faidherbia albida , have high digestibility values (43.1% − 62.8%) and metabolizable energy above 2200 kcal/kg DM. Blighia sapida , in particular, stands out with an exceptional dMO content of 62.8% and an energy value of 2657.6 kcal/kg DM, combined with values of 0.93 UFL and 0.88 UFV. However, this performance resulted in the highest methane production (505 mL CH₄/kg DM). Species with moderate levels of secondary metabolites, such as Piliostigma thonningii , Daniellia oliveri , Combretum collinum , Annona senegalensis and Diospyros mespiliformis , have average digestibility (53.3%) and energy values ranging from 1868.3 to 2206.4 kcal/kgDM. These plants offer a good compromise between digestibility and methane production through the balanced presence of polyphenols and flavonoids. This study definitively demonstrates that the rational management of secondary metabolites in ruminant feed is a promising way to combine zootechnical performance with a more responsible environmental footprint. This research is the first study in Benin that provides data and tables to guide cattle farmers in ecofeed rations formulation.