Study On The Regulation Of Colony Growth And Mycotoxins Production Of Aspergillus Parasiticus And Penicillium Viridicatum From Feed Sources

Aflatoxin and ochratoxin are the most common mycotoxins found in feed around the world.aflatoxin B₁（AFB₁）,aflatoxin B₂（AFB₂）,aflatoxin G₁（AFG₁）and aflatoxin G₂（AFG₂）in the aflatoxin family and ochratoxin A（OTA）in the ochratoxin family are the most toxic and harmful,posing a serious threat to animal health and animal husbandry development.At present,a large number of studies have only focused on AFB₁ in feed,but four aflatoxins are usually detected simultaneously in feed,and the Aspergillus parasiticus（A.parasiticus）can produce four aflatoxins at the same time.OTA is second only to aflatoxin in toxicity,and Penicillium viridicatum（P.viridicatum）is the main toxin-producing strain of OTA.Most of the available research has focused on chemical and biological detoxin production strategies for aflatoxin and ochratoxin.However,due to the strong chemical stability of aflatoxin and ochratoxin,they are difficult to eradicate in feed,and there is no safe and effective way to remove these two types of mycotoxins from contaminated feed.Therefore,how to inhibit the growth and toxin production of A.parasiticus and P.viridicatum from the source is the key issue to prevent their contamination of feed.This study focused on the A.parasiticus and P.viridicatum.The main factors（pH,temperature,humidity,feed nutrients and chemical pesticides applied,etc.）leading to mildew in the field management and storage stage of feed were selected,and the pH,temperature and humidity were adjusted with synthetic medium as the matrix,the main nutrients in the feed and the chemical pesticides commonly applied in the field were added,the growth status of the two fungal colonies was monitored,and the content of aflatoxin and ochratoxin in the medium was determined.Based on the results of univariate experiments,the response surface methodology was used to design the interaction test,and a model of the interaction of each factor on the growth and toxin production of the two fungi was established,so as to obtain the optimal conditions for inhibiting the growth and toxin production of the two fungi.The results of this study can provide a theoretical basis for effective prevention and control of aflatoxin and ochratoxin pollution in feed,and provide practical reference for ensuring forage safety,livestock and human health,and national economic security.The main findings are as follows:（1）Among the field management factors of forage crops,environmental pH and chemical pesticide application can affect the colony growth of A.parasiticus.The weakly alkaline（pH = 8）environment can significantly inhibit the colony growth of A.parasiticus.Among chemical pesticides,the fungicides difenoconazole,tebuconazole and mancozeb had inhibition rates of 59.89%,100% and 100% on the colony growth of A.parasiticus at the recommended concentration（R）in the field.However,the simultaneous addition of mancozeb and the insecticide chlorantraniliprole at R concentration reduced the inhibition rate of colony growth by 8.81%.The simultaneous addition of tebuconazole and chlorantraniliprole at R concentration reduced the inhibition rate of colony growth by 56.32%.The simultaneous addition of tebuconazole and the plant growth regulator gibberellin-indoleacetate-brassinolide at R concentration reduced the inhibition rate of colony growth by 41.24%.（2）Among the storage management factors of feed,environmental conditions,feed nutrients and chemical pesticide residues can affect the growth and toxin production of A.parasiticus.When the temperature and water activity dropped to 10℃ and 0.85 aw and below,respectively,the growth and toxin production of A.parasiticus were significantly inhibited.Glucose,fructose,sucrose,aspartic acid and proline in feed nutrients can significantly promote the growth and toxin production of A.parasiticus,and A.parasiticus preferentially uses carbohydrates as the initial substrate for toxification.Among chemical pesticides,when the residue of the fungicide chlorothalonil is lower than the maximum residue limit of pesticides in China,it can still significantly promote the growth and toxin production of A.parasiticus.The interaction between the residual fungicide tebuconazole and the plant growth regulator amine fresh fat-ethephon significantly reduced the inhibition rate of A.parasiticus colony growth.（3）Among the field management factors of forage crops,environmental pH and chemical pesticide application can affect the colony growth of P.viridicatum.A weakly alkaline（pH = 8）environment significantly inhibits colony growth of P.viridicatum.Among the chemical pesticides,the fungicide prochloraz inhibited the colony growth of P.viridicatum at R concentration of 100%.However,the simultaneous addition of prochloraz and herbicide chipton at R concentration reduced the inhibition rate of colony growth by 26.48%.The simultaneous addition of prochloraz and plant growth regulator gibberellin-indoleacetate-brassinolide at R concentration reduced the inhibition rate of colony growth by 22.97%.（2）Among the storage management factors of feed,feed nutrients and chemical pesticide residues can affect the growth and toxin production of P.viridicatum.P.viridicatum can still grow under the interaction of low temperature 4℃ and low water activity of 0.8 aw,and it is difficult to prevent its growth by controlling temperature and humidity.Starch,glucose,fructose and sucrose in feed nutrients can significantly promote the growth and toxin production of P.viridicatum,and P.viridicatum preferentially uses crude fat and sugar as the initial substrate for its toxicity,and finally uses starch,but in crops with high starch content,P.viridicatum will use starch and other carbon sources as the initial substrate for its toxicity.Among chemical pesticides,when the residue of the fungicide tebuconazole is lower than the maximum residue limit of pesticides in China,it can still significantly promote the growth and toxin production of P.viridicatum.The interaction of the residual fungicide prochloraz,the herbicide tribenuron-methyl and the plant growth regulator paclobutrazole-methylpiperium all promoted the growth and toxin production of P.viridicatum.In summary,during the field management period of feed crops,on the basis of ensuring the healthy growth of crops,timely adjustment of environmental pH and reasonable application of different types of chemical pesticides can effectively inhibit the growth and toxin production of A.parasiticus and P.viridicatum.During feed storage,controlling the ambient temperature and humidity,paying close attention to the feed types that are easily contaminated by mycotoxins,classifying feed with large differences in nutrient types and contents,and monitoring chemical pesticide residues in feed in real time can effectively prevent the growth and toxin production of A.parasiticus and P.viridicatum.The results of this study will provide new ideas for the prevention and control of mycotoxin pollution in feed from the source,and are of great significance for ensuring feed safety,promoting animal husbandry and national economic development.