Effects Of Residues Of Atrazine And Its Major Metabolites In Feed On The Safety Of Raw Milk

Atrazine is an inner absorption type herbicide widely used in corn production. The purpose of this study was to provide the base for evaluating the effects of atrazine and its major metabolites(T-ATZ) in dairy cattle feed on the safety of raw milk. Focusing on the critical points of the food chain, the studies were conducted on the T-ATZ pollution level in dairy cattle feed and raw milk, their degradation and left over pattern of T-ATZ between them by monitoring of T-ATZ in drinking water, corn silage, supplementary feed and raw milk from practical production.1. The development and validation of the LC-MS/MS methods for simultaneous determining atrazine and its six metabolites (DEA, DIA, DACT, HA, DEHA and DIHA) in drinking water, corn silage, supplementary feed and raw milk. All of the basic performance parameters of the methods, LOD, LOQ, recovery and precision could meet the requirements of EU SANCO12495-2011.2. Preliminary study on the existing forms and residue levels of T-ATZ in drinking water, corn silage, supplementary feed used in practical production was conducted by analyzing different kinds of samples collected from A, B and C regions.The results of T-ATZ showed that ATZ and DEA accounted for the major residues of the cow drinking water, but their concentrations were much lower than all existing MRL standards. In corn silage, DEHA accounted for a greater proportion of the metabolites than HA; DEA and DIA can only be found in a few of samples. In supplementary feed, ATZ and DEHA,HA,DEA residues could be found in all collected samples; HA made the major proportion of the residues, ATZ, DEHA and DEA could also be found and the their concentrations were almost the same. In contrast to the residual results of A and B region, the residual level of C region was significant higher.3. Study on the degradation and transition of T-ATZ during corn ensilage and the silage storage.Two experiments were conducted for the ensiling fermentation. One was adding ATZ compound directly to blank corn straw before ensilage. Another was using corn straw with natural T-ATZ residues for the ensilage. The results indicated ensilage and using ensilage agent in the process could efficiently decrease ATZ and its dealkylated metabolites with high toxicity in corn silage and improve the security of the crude feed. The study of degradation and transition during silage storage illustrated the total concentration of T-ATZ still decreased, but after90days from the silo opening, the changes were slowdown. T-ATZ more liked to degrade into the low toxicity form.4. To confirm the major existing forms and residue levels of T-ATZ in dairy cattle diet and in the raw milk, the practical production of nine dairy farmers in the Lang Fang district were monitored at two periods. And the residual regular patterns of T-ATZ in raw milk were studied based on the results.The monitor Data demonstrated either in the initial period or in4months of the silage silo opening, silage feed in the diet was the major source of T-ATZ of the milk. As time went on, the effects from the supplementary feed would grow up. In the initial period major residues in feeds (including silage and supplementary feed) were ATZ and HA, while in the second period DEHA accounted for a large proportion of the residues, DEA kept a higher residual proportion in the two periods. For the raw milk, HA, DEA and ATZ were the major residual forms. But with passing of time, DEA level increased gradually and became the most pollutant in the second period.The study illustrated:when the residue level of ATZ and its dealkylated metabolites in feed was high, their transfer rate to the raw milk was1.02%, but when the level was low, their transfer rate was5.21%. It seems that the concentrations of ATZ and its dealkylated metabolites in raw milk might be able to exceed10μg/kg which is the MRL value of Australian. Obviously, ATZ and its dealkylated metabolites in feed were a critical potential safety hazards to the raw milk.As to the HA, the maximum transfer rate from feed to raw milk was1.02%and the highest level in milk monitored in this study was2.35μg/kg. Obviously, HA in feed did not pose a threat to milk since the toxicity of HA is much lower than ATZ.