The Occurrence Of Organophosphate In Protein Feed And Its Migration And Metabolism In Laying Hens

Organophosphate esters（OPEs）are a kind of additive flame retardants which are widely used.OPEs might be persistent,toxic,and bioaccumulative in environment as the persistent organic pollutants（POPs）.However,unlike POPs,OPEs might enter animals through a protein-associated pathway.Animal feed is the main food for farmed animals.The pollutants in animal feed are prone to bioaccumulate in the food chain.Therefore,feed contamination is a threat to food safety of animal origin.Compared with environmental media,food,wildlife and humans,OPEs have not been studied in animal feed.In this research,OPEs and their organophosphate diesters（di-OPEs）metabolites were studied in animal protein feeds to figure out their occurrence and distribution patterns.Furthermore,the metabolic process of OPEs in chickens was studied by exposure experiment.To do so,the following research works were carried out:At first,high performance liquid chromatography-tandem mass spectrometry was used to establish the analytical methods of OPEs and di-OPEs in eight plant-derived and animal-derived feeds,and in tissues of laying hens.The recovery,precision and accuracy of OPEs and di-OPEs were satisfied in plant-derived and animal-derived feeds and in tissues of laying hens.Second,we investigated the occurrence of OPEs in animal protein feeds.As far as we know,there is no study investigating OPEs in animal feed yet.OPEs were detected in all the plant-derived and animal-derived feeds in this study.The concentrations of OPEs in the plant-derived and animal-derived feeds ranged from 12.6 to 301 ng/g（dry weight,dw）.The highest level of OPEs was found in meat meal,followed by feather meal,plant-derived feeds,blood meal.Currently,plant-derived feeds are important sources for livestock exposing to OPEs.The source of OPEs in feather meal and plant-derived feeds might be related to dust adhesion.Different plant-derived and animal-derived feeds had different OPEs congeners distribution.Plant-derived feeds and blood meal were dominated by tris（2-chloropropyl）phosphate,and meat meal and feather meal were by tris（2-chloroethyl）phosphate and triphenyl phosphate.Tri-n-butyl phosphate and tri-isobutyl phosphate were found statistically significant correlated in all animal protein feeds.Such a strong correlation may indicate common sources or similar environmental fates.Thirdly,di-OPEs,the main metabolites of OPEs in animal protein feeds were studied.In this research,theΣ₈di-OPEs concentrations were between 1.98-182 ng/g dw in plant-derived and animal-derived feeds.The highest level of di-OPEs was found in meat meal（52.1 ng/g dw）,followed by blood meal（49.9 ng/g dw）,feather meal（23.3 ng/g dw）and plant-derived feeds（18.3 ng/g dw）.The concentrations of di-OPEs were on the same order of magnitude as OPEs in animal protein feeds.The dimethyl phosphate dominated in meat meal,while bis（1,3-dichloro-2-propyl）phosphate dominated in the blood meal,feather meal and plant plant-derived feeds.The ratios of di-OPEs/OPEs in plant-derived and animal-derived feeds were usually higher than 1,indicating that the transformation products of di-OPEs may also contribute to the animals’exposure as well as the maternal OPEs.The similar di-OPEs/OPEs values in animal protein feeds and dust samples indicated that dust may be an exogenous source of OPEs in some animal protein feeds matrices.Finally,we studied metabolism of tris（2-chloroethyl）phosphate（TCEP）in chicken through contaminated feed consumption.It was found that the level of TCEP in the liver was 194 times higher than that in egg yolk during the exposure period,and TCEP had obvious bioaccumulation in the liver.During the clearance period,TCEP concentration tended to be stable at 17 days in all tissues.The liver was the target organ of TCEP,which may be due to it was responsible for the detoxification,metabolism,and excretion of exogenous chemicals.