Medicinal and Aromatic Plants as Feed Additives: a Scoping Review of the Economic, Environmental and Social Sustainability of Livestock Systems

Growing concern about antimicrobial resistance and efforts to reduce the use of antibiotic growth promoters have increased interest in phytogenic feed additives. Among these, medicinal and aromatic plants (MAPs) have been investigated for their potential effects on animal performance, health, and product quality. However, the extent to which the literature also addresses their sustainability remains unclear. This scoping review mapped the available evidence on the environmental, economic, and social dimensions of using MAPs as feed additives in terrestrial livestock systems. Literature searches were conducted in Scopus and Web of Science using equivalent search strategies adapted to the syntax of each database. Each strategy comprised three conceptual blocks: medicinal and aromatic plants and phytogenic additives, animal nutrition, and sustainability. The selection process was documented using a PRISMA flow diagram. Of the 2,169 records initially identified, 468 duplicates were removed, 1,701 records were screened, and 144 publications underwent full-text assessment. The final corpus comprised 56 records. Data were extracted on study characteristics, animal and plant species, formulation, dosage, and treatment duration. For each sustainability dimension, evidence was classified according to operational criteria as direct, indirect, or not assessed. Fifty records included an in vivo component, while the remaining six comprised four reviews and two meta-analytic studies. Most publications were recent and focused on poultry: 37 records (66.1%) were published between 2021 and 2026, and 40 included at least one poultry group. The environmental dimension was the least represented, with 5 records (8.9%) reporting direct evidence and 12 (21.4%) reporting indirect evidence. The main indicators concerned methane, ammonia in excreta, nitrogen utilisation and excretion, and mineral excretion. For the economic dimension, 13 records (23.2%) used direct monetary indicators, 39 (69.6%) reported production-related proxies, and 4 did not assess this dimension. The social dimension was predominantly animal-centred: 5 records (8.9%) reported direct animal health or welfare outcomes, 50 (89.3%) reported indirect links, and 1 did not assess this dimension. No record directly assessed farmers, workers, or consumers. Specific MAPs, doses, and experimental conditions were associated with potential environmental, economic, or health benefits, but the findings were heterogeneous and cannot be generalised. None of the 56 records directly and jointly assessed all three sustainability dimensions. Major gaps included life-cycle and supply-chain assessments, long-term economic analyses, and studies of stakeholder acceptance, adoption, and preferences. The available evidence therefore suggests that MAPs may contribute to livestock sustainability but does not yet demonstrate their overall sustainability. Future research should therefore assess the three dimensions jointly under real farming conditions and investigate MAP adoption by farmers and consumer acceptance of animal products obtained using these additives.