Along the coast of West Africa, grazing ruminants rely on perennial forage species remaining in uncultivated plots, roadsides, and marshlands during the dry season. To assess the quality of these forages, thirteen drought-tolerant plants were harvested at the mature stage, and the samples were evaluated for chemical composition, in vitro fermentation characteristics, and metabolizable energy (ME) content. They are ten drought-tolerant grasses, including: Andropogon virginicus, Brachiaria deflexa, Cenchorus biflorus, Dactyloctenium aegyptium, Eragrostis tremula, Leptochloa caerulescens, Loudetia aroundinacea, Paspalum notatum, Paspalum vaginatum, Pennisetum purpureum, two perennial herbs, Chamaecrista rotundifolia, Zornia latifolia, and one multipurpose tree, Elaeis guineensis. Legume species had the highest nutritional value (highest crude protein and ME, and lowest neutral detergent fiber) of the species studied. In terms of the in vitro data, the gas produced after 120 h of incubation ranged from 149 mL/g in E. tremula to 185 mL/g in Paspalum. Z. latifoliaa and had the fastest rate of fermentation, producing half of the total gas in 19.5 h, whereas E. tremula required 49.9 h (p < 0.01). The production of branched-chain fatty acids (isobutyrate and isovalerate) was greatest for E. guineensis and the lowest in both Paspalum species (p < 0.01). The study suggests the need for the protein supplementation of the animals to ensure maximum forage utilization and to satisfy the nutrient requirements of ruminant livestock.
Keywords: Andropogon virginicus; Cenchrus biflorus; Zornia latifolia; animal feeding; drought-tolerant plants; drylands; in vitro organic matter degradability; sustainable urban agriculture; volatile fatty acids.