Pesticide residues in animal feed: emerging risks for animal health and crop production

Abstract

Pesticides are essential for maximizing crop yields and ensuring food security, yet concerns are growing about their accumulation in the food chain. While human dietary exposure has received considerable attention, pesticide residues in animal feed represent a critical, underexplored pathway that can affect livestock health and crop production through the reuse of contaminated manure. This review examines these emerging risks by focusing on livestock health and the cascading effects on crops. Following PRISMA 2020 guidelines, we systematically searched and synthesized literature addressing: (i) prevalence, types, and concentrations of pesticide residues in feed; (ii) toxicological effects on livestock; and (iii) environmental carryover potential via manure application to soils. Residues of major pesticide classes carbamates, organochlorines, organophosphates, and pyrethroids frequently enter feed through treated crops, pre-harvest desiccation, and environmental persistence. While EFSA concludes that typical exposure levels do not pose major acute risks to animal health, significant uncertainties remain regarding chronic low-dose exposures and synergistic effects of multi-residue mixtures on livestock physiology. Evidence on toxicological effects is drawn from a mixture of feed-specific, laboratory-animal, and human studies; the source of evidence for each finding is now explicitly identified throughout the Results (Section 3.3, Table 3). Experimental and field studies demonstrate that pesticide residues transfer from feed to manure and, subsequently, to soil when manure is used as fertilizer. This circular pathway creates secondary contamination, where residues are taken up by crops, causing phytotoxicity, reduced germination, and diminished performance. These findings underscore the need for strengthened regulatory frameworks addressing cumulative and carryover effects, alongside enhanced monitoring. From a One Health perspective, mitigating these risks requires broader adoption of sustainable practices, including Integrated Pest Management (IPM), safer pre-harvest protocols, and improved manure waste management to break the contamination cycle and protect animal, environmental, and human health.