Aflatoxin B₁ in Cattle Feed and Aflatoxin M₁ in Milk in Northern Nigeria: Occurrence, Feed-to-Milk Carry-Over, Health Implications and Research Gaps

Abstract

Aflatoxins are toxic fungal metabolites of major food- and feed-safety concern. In dairy production, aflatoxin B₁ (AFB₁) ingested in contaminated feed is metabolised to aflatoxin M₁ (AFM₁), which is excreted in milk. This narrative review synthesises evidence on AFB₁ in cattle feed and AFM₁ in milk, with emphasis on Northern Nigeria and Katsina State. Literature published principally between 2007 and 2025 was identified through PubMed, Scopus, Google Scholar and African Journals Online and was critically interpreted with attention to analytical method, matrix, regulatory benchmark and study design. Northern Nigerian evidence demonstrates substantial contamination: Omeiza et al. (2021) detected AFB₁ in 89% of 180 cattle-feed samples and AFM₁ in 94% of 180 cow-milk samples, while a 2025 Katsina study by Olanrewaju and Okunola reported AFB₁ and AFM₁ in all sampled feed and milk, respectively. These studies establish that paired feed–milk investigation has already been undertaken; the remaining needs are larger and more representative Katsina datasets, repeated seasonal sampling, clearer animal- or herd-level pairing, harmonised analytical quality assurance and stronger characterisation of feed storage and management. Differences among ELISA, TLC and chromatographic methods, together with inconsistent reporting units in parts of the literature, limit direct comparison. Future work should integrate validated HPLC-FLD or LC-MS/MS methods, seasonal sampling, feed-management data and exposure assessment to support practical prevention and regulatory surveillance.