Occurrence of aflatoxin B1 in total mixed rations and aflatoxin M1 in raw and commercial dairy milk in northern China during winter season

This study aims to investigate the occurrence of aflatoxin B1 (AFB1) in total mixed rations (TMR) and aflatoxin M1 (AFM1) in raw and commercial milk in northern China during winter season. A total of 22 feed samples, as well as the corresponding 84 raw milk and 69 commercial milk samples were randomly collected from north-west, northeast and north areas of China from November 2019 to January 2020. High performance liquid chromatography and enzyme linked immunosorbent assay method were applied to detect AFB1 and AFM1. All samples presented AFB1 (30?370 ng/L) and AFM1 (10?430 ng/L) levels under the legal limit of China for raw milk (10 ?g/L) and commercial milk (500 ng/L). While 31.8% of TMRs and 34.5% of raw milk samples exceeded the European Union (EU) legal limit for AFM1 in raw milk (5 ?g/L) and commercial milk (50 ng/L). Compared with the samples from northeast and north areas of China with the similar AFB1 concentration, samples from northwest area of China exhibited higher AFM1 level (mean = 130 ng/L), thus presenting a higher transfer ratio from AFB1 to AFM1. A Linear relationship was observed between AFB1 in TMRs and AFM1 in raw milk. In conclusion, all samples from northern China presented AFB1 and AFM1 levels under Chinese legal limit and only about 30% of the tested samples exceeded the EU legal limit. However, the aflatoxin contamination in northwest area of China should be paid more attention to due to the high AFM1 levels and high variance in milk samples.

Automated summary

In this study, the occurrence of aflatoxin B1 (AFB1) in total mixed rations (TMR) and aflatoxin M1 (AFM1) in raw and commercial milk in northern China during winter season was investigated. Results showed that all samples from northern China were below the legal limit for AFB1 and AFM1 in raw and commercial milk, with only about 30% of samples exceeding the EU legal limit. However, the northwest area of China had higher AFM1 levels and variance in milk samples, indicating a need for more attention to aflatoxin contamination in this region.