Nutrition, Environment and Sustainability in Smallholder Poultry Systems: A Critical Narrative Review

Abstract

Poultry keeping is undertaken by the majority of rural households across low- and middle-income countries, yet the nutritional, environmental and health dimensions of smallholder systems remain fragmented across disciplinary literatures that rarely engage with one another. This critical narrative review synthesises evidence on three interlocking themes: the nutritional adequacy of scavenging and locally sourced feed resources; the environmental and climatic stressors, principally heat stress and genotype-by-environment interaction, that constrain productivity; and the bidirectional relationship between smallholder poultry keeping and human nutrition, including the underappreciated tension between the nutritional benefits of poultry-derived foods and the infection-related risks of close human-poultry contact. Literature was identified through structured searches of multidisciplinary and subject-specific databases, supplemented by citation tracking, and appraised for methodological quality, source credibility and relevance rather than citation volume alone. The review finds that the scavenging feed resource base is consistently deficient in protein, calcium and several micronutrients, a finding replicated across geographically disparate settings over three decades, and that locally available alternative feedstuffs and non-conventional protein sources, including insects and agro-industrial by-products, offer only partial and context-dependent solutions. Evidence on genotype-by-environment interaction indicates that tropically adapted breeds outperform indigenous ecotypes and imported exotic genotypes under smallholder conditions, although matching genotype to agroecology remains imperfectly operationalised in practice. Disease control interventions, particularly Newcastle disease vaccination, generate consistent productivity gains, yet translation into improved child nutritional status is not guaranteed and depends on household decisions about consumption versus sale. A parallel and only partially reconciled literature indicates that close domestic exposure to poultry and their faeces is associated with diarrhoeal disease, environmental enteric dysfunction and, in some settings, growth faltering, complicating straightforward advocacy for poultry-based nutrition-sensitive agriculture. Confidence in specific causal pathways remains constrained by observational designs, heterogeneous exposure measures and limited longitudinal evidence. The review identifies priority research needs in integrated genotype-nutrition-environment trials, hygiene-sensitive poultry interventions and mycotoxin risk management, and concludes that smallholder poultry development strategies must be locally tailored rather than assuming uniform benefit across agroecological and sociocultural contexts.