Aflatoxin B1 contamination and fungal diversity in oilseed cakes and formulated feeds from livestock feed markets in Addis Ababa and surrounding areas

This study was conducted in Addis Ababa, surrounding peri-urban and urban feed markets to assess the prevalence of aflatoxin B1 (AFB1) and identify fungal diversity in livestock feeds. Two hundred and ninety samples of oil seed cakes and formulated feeds were collected from the randomly selected feed vendors. The samples were analysed for aflatoxin B1 using a Helica® Aflatoxin B1 (low matrix) Enzyme-linked immunoassay (ELISA) kit. To validate the ELISA results, a subset of randomly selected samples was further analysed using High-performance liquid chromatography-fluorescence detection (HPLC-FLD). The results indicated that 92% of poultry ration, 72% of dairy ration, 66% of linseed cake, 64% of noug seed cake, 61% of cotton seed cake, and 36% of soybean cake were contaminated with AFB1 exceeding the permissible level (20 µg/kg) in Ethiopia. To evaluate fungal diversity, genomic DNA was extracted, pooled by feed type, and sequenced. The findings revealed variations in the diversity indices of fungal phyla, families, genera and species. The Metabarcoding results revealed Ascomycota as the dominant phylum in all feeds, with Aspergillaceae, Nectriaceae, Botyosphaeriaceae, and Cladosporiaceae being the dominant families. Aspergillaceae accounts for 53%, 43%, 16%, 33%, 11%, and 28% of the total fungal contamination detected in cotton seed cake (S1), noug seed cake (S2), soybean cake (S3), linseed cake (S4), poultry ration (S5), and dairy ration (S6), respectively. The synergistic presence of multiple fungal species, some of which are known to be harmful, was identified in the feed samples. Among the species, the proportion of Aspergillus flavus found was 1.8%, 3.8%, 0%, 0.4%, 1.2%, and 1.2% in the feeds S1–S6, respectively. The findings highlight the critical need for enhanced feed management practices, improved education and training for feed handlers on feed safety, stricter regulatory measures, and more research on mycotoxins mitigation.