Nutritional Value and Utilization of Conventional and Hydroponic Sorghum with Cowpea in Goats - A Critical Narrative Review
Francisco Kanyinji *
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Probby Chisenga
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Prudence Simfukwe
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Brian Simakando
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Simushi Liswaniso
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Oswin C. Chibinga
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Born Ngándu
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Sharon Nyimbili
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
Katai J. Simukonda
Department of Animal Science, School of Agricultural Sciences, University of Zambia, Lusaka, Zambia.
*Author to whom correspondence should be addressed.
Abstract
Seasonal forage shortages constrain tropical goat production and encourage interest in sorghum, cowpea and hydroponic fodder. Their feeding value, however, depends on usable nutrient supply rather than fresh biomass alone. This critical narrative review evaluates conventional and hydroponic sorghum, cowpea supplementation, and their implications for intake, digestibility, nitrogen utilisation, methane and smallholder adoption. Selected primary studies and supporting reviews were interpreted according to crop identity, animal species, comparator, experimental design and measurement method. Sorghum production studies demonstrate variation among cultivars and harvest stages, but do not establish a consistent productive advantage from sprouting. Evidence from other sprouted cereals supports further goat trials, although ration substitution confounds attribution to germination. Cowpea can supplement nitrogen-deficient cereal forage; responses vary with preservation, energy supply and inclusion level. A maintenance-goat study illustrates this trade-off: increasing cowpea silage replacement reduced intake and dry-matter digestibility, whereas an intermediate treatment improved nitrogen balance expressed relative to intake. Methane findings require particular caution because batch-incubation results, laser-derived estimates and directly measured daily flux are different endpoints. Cyanogenic potential, feed hygiene, dry-matter recovery, seed opportunity cost and upstream resource use also influence feasibility. The evidence supports nutritionally balanced, locally evaluated sorghum–cowpea diets rather than a universal mixture or assumed methane benefit. Research should connect replicated fodder production with digestible-nutrient intake, nitrogen partitioning, sustained animal performance and full production costs.
Keywords: Sorghum bicolor, Vigna unguiculata, hydroponic fodder, goat nutrition, nitrogen balance, enteric methane