Outbreak of aflatoxicosis in a dairy herd induced depletion in milk yield and high abortion rate in Pakistan

This case report investigated the outbreak of aflatoxicosis in a dairy herd in Pakistan, which resulted in 30 abortions of 40 confirmed (75%) pregnant cows in a period of 35 days and in 18.8% depression of farm average milk production for the entire herd. The analysis of the concentrate feed of the total mixed ration (TMR), using enzyme-linked immunosorbent assay (ELISA) procedures from two different local laboratories, indicated concentrations of 60 μg/kg dry matter (DM) of aflatoxin B1 (AFB1) and 100 μg/kg DM of total aflatoxins (AFs: sum of B1, B2, G1 and G2). Subsequently, a confirmatory analysis with a more sensitive and validated multi-metabolite liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was performed. This analysis detected a concentration of total AFs in the TMR of 166 μg/kg DM ± 3.5 (AFB1:134, AFB2:17.4 and AFM1:14.9 μg/kg DM). The concentrate feed (55% of the TMR DM) was confirmed as a source of contamination, presenting a concentration >29 times higher than the EU-maximum limit value (5.68 μg/kg DM). Additionally, the multi-mycotoxin analysis evidenced the co-occurrence of 81 other toxic and potentially toxic fungal metabolites in the fed TMR. After replacing the contaminated concentrate feed with feedstuffs of the same formulation but from a new charge of ingredients, the abortion episodes ceased, and milk production increased significantly. In conclusion, the data of this case report suggest that AFs may be associated with pregnancy losses in dairy cattle and milk production depression. From the public health perspective, the data also indicate the need for a more careful examination of dairy animal feed in Pakistan. Since the high concentration of AFB1 detected in feed and considering the literature-reported transfer rates (1-6%) of this toxin to AFM1 (carcinogen for humans) in milk, the milk produced during the outbreak period is expected to be contaminated with AFM1, which raises public health concerns.