Metabolomics Analysis Of The Effects Of Pure Aflatoxin B1 Addition And Naturally Contaminated Feed On Dairy Cows Health And Milk Quality

Metabolomics can detect changes of metabolites with low molecular weight.Therefore,it can be used to study the constituents and variation of the metabolites produced by stimulation of environmental,pathological,physiological infector or gene change.This is a new subject that is developing in the post-genomic era and is also an important part of system biology.At present,it has been widely used in physiology,pathology,pharmacology,botany and other fields,however,few researches have been done on dairy animal safety and quality in milk products.Along the continuous development of relevant research fields,the research on the nutrition,safety and quality of dairy cows will play an important role in the fields.The present study examines the effects on dairy cows health and milk quality though pure aflatoxin B1 addition and naturally contaminated feed.The study was divided into three parts.1.Biological system responses of dairy cows to aflatoxin B1 exposure revealed with metabolomic changes in multiple biofluids.Research on mycotoxins now requires a systematic study of post-exposure organisms.In this study,the effects of aflatoxin B1(AFB1)on biofluids biomarkers were examined with metabolomics and biochemical tests.The results showed that milk concentration of aflatoxin M1 changed with the addition or removal of AFB1.AFB1 significantly affected serum concentrations of superoxide dismutase(SOD)and malon dialdehyde(MDA),SOD/MDA,and the total antioxidant capacity.Significant differences of volatile fatty acids and NH3-N were detected in the rumen fluid.Eighteen rumen fluid metabolites,11 plasma metabolites,and 9 milk metabolites were significantly affected by the AFB1.These metabolites are mainly involved in the pathway of amino acids metabolism.Our results suggest that not only is the study of macro-indicators(milk composition and production)important,but that more attention should be paid to micro-indicators(biomarkers)when assessing the risks posed by mycotoxins to dairy cows.2.Biochemical and metabolic profiles of dairy cows with mycotoxin-contaminated diets.Most previous studies were focused on the effects of mycotoxins on biochemical profiles or products in dairy ruminants.Thus,it is necessary to study the changes in metabolism that occur after exposure to mycotoxins,as well as biochemical changes.We measured the biochemical and metabolic changes in dairy cows after exposuring to mycotoxins based on biochemical analyses and nuclear magnetic resonance.Twenty-four dairy cows were randomly assigned to three groups.Cows received uncontaminated diets were set as control group,including 2 kg of uncontaminated cottonseed.Cows in the 50%replacement group received the same diet as the control group,but with 1 kg of uncontaminated cottonseed and 1 kg of cottonseed contaminated with mycotoxins.Cows in the 100%replacement group received the same diet as the control group,but with 2 kg of mycotoxins contaminated cottonseeds.The results showed that the serum ?-glutamyl transpeptidase content and total antioxidant capacity were significantly affected by cottonseeds contaminated with mycotoxins.There were also significant differences in the isovalerate and NH3-N levels.Eight plasma metabolites differed significantly among the three groups.These metabolites were mainly involved in amino acid metabolism pathways.Therefore,the results suggested that amino acid metabolism might be affected by exposure to mycotoxins.3.Evaluation of influences of mycotoxins-contaminated diets on milk profiles and metabolites in dairy cows.Mycotoxins are key factors in food and feed safety.However,most previous studies about dairy ruminants were focused on the biochemical parameters or production.Little is known about the milk micro-profiles,such as fatty acids and amino acids,under mycotoxin exposure.With taking advantage of the well-established gas chromatography and NMR(Nuclear magnetic resonance)analyses,milk micro-profiles and metabolic changes of dairy cow were measured after mycotoxins exposuring.The results showed that milk compositions were unchanged,but milk aflatoxin M1 concentration changed along with the mycotoxins addition or clearance.Cottonseeds contaminated with mycotoxins had a significant reduction in milk unsaturated long chain fatty acids,but there was no influence on the content of short and medium chain fatty acids.Interestingly,contaminated feed did not reduce the content of milk amino acids.Twelve metabolites showed significant differences among the three groups.These metabolites are mainly involved in the metabolic pathways of phenylalanine,tyrosine and tryptophan biosynthesis,phenylalanine metabolism and valine,leucine and isoleucine biosynthesis,which might indicate that amino acid metabolism was influenced by mycotoxins.In conclusion,these results suggest that the studies should not only on milk composition,but also on pay attention to micro-indicators(fatty acids and amino acids)of dairy cows caused by mycotoxins.