Efeito sazonal da contaminação por aflatoxinas B 1 e M 1 em propriedades leiteiras na região Sul do Rio Grande do Sul, Brasil

Abstract

Aflatoxins are toxic compounds which are yielded by the secondary metabolism of some fungal species, such as Aspergillus flavus, A. parasiticus and A. nomius, that

contaminate agricultural products which are widely used for human and animal consumption. Aflatoxins B 1 (AFB 1 ), B 2 (AFB 2 ), G 1 (AFG 1 ) and G 2 (AFG 2 ) are some of the contaminants. Aflatoxin M 1 (AFM 1 ), which is a hydroxylated metabolite

of AFB 1 , can be found in milk produced by dairy cows that have eaten feed contaminated with the latter. It poses risks to human health since it has mutagenic, teratogenic and carcinogenic properties. This study aimed at evaluating

AFB 1 , AFB 2 , AFG 1 and AFG 2 in samples of feed eaten by dairy cows, besides AFB 1

and AFM 1

in samples of raw milk; the seasonal effect was analyzed

and

the estimate of human exposure to aflatoxin was based on estimates of daily intake in milk. Feed samples were collected on a dairy farm located in the south of Rio Grande do Sul (RS) state, Brazil, in four occasions that referred to the seasons of the year, when milk samples were collected from every cow. Seventy-three samples were collected (winter, n= 15; spring, n= 20; summer n= 16; fall, n= 22). Raw milk samples were collected in cold storage tanks (n= 23) on other farms which are also located in the south of RS. Feed samples were taken to the SAMITEC Institute (Analytical, Microbiological and Technological Solutions) so as to have AFB 1 , AFB 2 , AFG 1 and AFG 2 analyzed by Liquid Chromatography coupled with Mass Spectrometry. Mycotoxins were extracted from milk by the QuEChERS method and quantified by High-Performance Liquid

Chromatography (HPLC) with fluorescence detection. Resulting data on contamination by aflatoxins in milk samples led to the evaluation of population exposure as the result of milk intake. AFB 1 levels were found in feed collected in summer, fall and winter, at 1.0, 1.0 and 1.6 µg kg -1 , respectively, while the other aflatoxins were not detected. There was no contamination in the sample collected in spring. About 95% of milk samples (individual and tanks) were contaminated by AFM 1

in the range from 0.2 to 1.47 µg L -1 , which is above the limit of aflatoxin in milk issued by the Brazilian legisl ation (0.5 µg kg mean of contamination by AFM 1 in milk samples collected individually from every

cow was found in winter (1.0 µg L -1 ), while mean concentration in the other seasons was around 0.5 µg L-1. AFB 1 was found in 6% (n= 6) of milk samples at concentrations that ranged from 0.09 to 0.37 µg L -1 . Based on the mean level of contamination by AFM 1 of samples collected in cold storage tanks (0.63 µg L - 1 -1 ), estimates of its daily intake were 3.0 ng/adult and 10.0 ng/child. These ealth by milk, mainly to children, since they consume high amounts of this product and are more susceptible

to contamination. Thus, the importance of controlling contamination by toxigenic fungi of agricultural products aimed at animal feed should be highlighted in order to avoid aflatoxin production.