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How do you prevent aflatoxins? Look! Harm and Prevention of Aflatoxin.

Posted on November 8, 2019 by Josephine

What’s aflatoxin?

Aflatoxin (abbreviated AF) is mainly a metabolite of Aspergillus flavus and Aspergillus parasiticus, may be present in foods and feed contaminated with Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are most susceptible to contamination of peanuts, corn, cottonseed, eggs, meat, milk, and dairy products in warm and humid climates. Wheat, sorghum and sweet potatoes, are less contaminated with aflatoxin. The pollution rate of aflatoxin in China's grain and feed is very high, which brings great losses to enterprises for feed and farming owners. The aflatoxin peanuts, aflatoxin corn and other aflatoxin food will endanger people health.

Physicochemical properties of aflatoxin

At present, 18 kinds of structures in aflatoxin, such as AFB1, AFB2, and AFM1, have been identified, and their basic structures all contain difuran ring and Oxacillin (also known as coumarin). The former is a toxic structure and the latter may be related to cancer. Aflatoxin is insoluble in water, hexane, ether and petroleum ether, and is easily soluble in organic solvents such as methanol, ethanol, chloroform, and dimethylformamide. The weight of the molecular is 312-346, the melting point is 200-300°C, and aflatoxin is resistant to high temperature. It usually has little damage under the heat treatment, and only be decomposed at the temperature of the melting point.

Aflatoxin can be rapidly decomposed by alkali, but the reaction is reversible. Ane it means that it is restored under acidic conditions. In general, Aspergillus flavus is easier to produce and multiple at the temperature of 30°C, the relative humidity of 80% and grain moisture of more than 14% (peanuts with above 9%moisture ). Aflatoxin produced the highest amount of toxicity between 24-34°C. Almost all grains, forages and various foods (including animal products) can be used as a substrate for producing Aspergillus flavus.

Look! Harm and Prevention in Aflatoxin.

The harm of aflatoxin to animals

Aflatoxin is highly toxic and is currently the most toxic substance in a mold. Among the 18 species of aflatoxin found, AFB1 is the most toxic one, AFM1 and AFG1 are the second, and AFB2, AFG2 and AFM2 are less toxic. The toxicity of AFB1 is 68 times that of arsenic, and the ability to induce liver cancer is more than 75 times that of dimethylnitrosamine. The toxicity of aflatoxin is varies depending on the species, age, sex and body condition of the animal, and the nutritional status. Young animals and male animals are more sensitive to aflatoxin.

Aflatoxin has effects on inducing mutation and inhibiting immunity and carcinogenesis. The target organ for aflatoxin mainly influences in the liver. Animal acute poisoning manifests as loss of appetite, movement disorders, cessation of excretion, hepatitis, jaundice, liver congestion, hemorrhage, swelling, degeneration and necrosis, accompanying severe vascular, central nervous system damage. And animals will even death within hours to days after acute poisoning. The early symptoms of chronic poisoning are poor appetite, weight loss, decreased performance, decreased carcass, and eggshell quality, and later jaundice, fatty liver, liver damage and inhibition of animal immune function and carcinogenesis.

Pig and aflatoxin

Pigs are sensitive to mycotoxins, especially breastfeeding or suckling piglets. In general, mycotoxins reduce feed intake, performance, and immune function when levels of mycotoxins are relatively low. 20-200 ppb of aflatoxin B1 can cause a decrease in feed intake and production capacity but can be offset by increasing the concentration of special dietary nutrients such as lysine or methionine. Severe aflatoxin poisoning (1000-5000 ppb) can occur acute effects, including effects on breathing. It has been reported that when the content of aflatoxin in the feed is 2.0 mg/kg, the weight of pig can be reduced from 33.7 kg to 29.7 kg in the control group. Aflatoxin can be transferred to the fetus through the placental barrier, causing fetal malformations and resulting in reduced litter size, weak births, stillbirths, and mummies. Abortion occurs in individual females with acute poisoning and aflatoxin poisoning in boar shows a decrease in libido.

Poultry and aflatoxin

Aflatoxins affect all breeds of poultry, leading to death at high levels of intake and harmfulness at low levels of intake. Young birds, especially ducklings and turkeys, are very sensitive to aflatoxin. In general, aflatoxins in the diets of the poultry of growing should not exceed 20 ppb. However, feeding a diet in poultry below 20 ppb still reduces the resistance to diseases and their ability to resist stress. Laying hens can tolerate higher levels of aflatoxin, but not more than 50 ppb. AFB1 mainly acts on the immune system, reducing the anti-stress ability to lay hens, reducing egg weight, producing not hard eggshells, and decreasing egg production. Feeding broilers with 2.0 mg/kg aflatoxin increased the mortality of broiler by 22.5%. Aflatoxin can destroy the sexual function of the cock, causing the testicle to shrink. And the seminiferous tubules are poorly developed, which hinders the production of semen. It has been found that egg yolks consumed by humans have metabolites of aflatoxin.

Cow and aflatoxin

Feeding aflatoxin-contaminated feed to the cow not only reduces their production capacity and physical fitness but also directly harms human health by milk with a metabolite, aflatoxin M1.

Beef cattle and aflatoxin

Although beef cattle are more tolerant of aflatoxins than pigs and poultry, aflatoxins have a great impact on them. Feeding beef with aflatoxin-contaminated feed can result in a decrease in growth rate and a higher ratio of meat in the feed. If the adult cattle ingest with high levels of aflatoxin, it can cause damage to their liver and inhibit immune function. In some cases, it can cause severe rectal fistula and rectal prolapse in calves. Acute poisoning in cattle can even lead to death.

Look! Harm and Prevention in Aflatoxin.

The harm of aflatoxin to human health

Aflatoxins are recognized as substances to cause liver cancer, of which AFB1 is the most carcinogenic kind. Consumption of foods containing low levels of aflatoxin in the long-term will damage the liver. The manifestation of acute aflatoxin poisoning has recently been reported in third world countries. The acute aflatoxin symptoms include vomiting, abdominal pain, pulmonary edema, convulsions, coma, cerebral edema, liver, kidney-shaped veins, and excessive heart fat and even death. In 1988, the International Agency for Research on Cancer (IARC) listed aflatoxin B1 as one of the human carcinogens. And it was confirmed that carcinogens by has positive effects on dietary aflatoxins and hepatocellular carcinoma (LCC) in many Asian and African epidemiologists. Besides, aflatoxin carcinogenesis to humans may be associated with age, gender, nutritional status, and hepatitis or parasitic infections. Shank et al.

(1972) investigated commercially available foods and cooked foods (meal) in a household in Thailand and calculated the average daily intake of aflatoxin per person. It was found that the high content of aflatoxin was consistent with the regional distribution in a high incidence of liver cancer. Corn and homemade peanut butter Philippine are heavily polluted aflatoxin. And the incidence of liver cancer in the area with staple food in corn or homemade peanut butter is more than 7 times than that of other areas. After eating aflatoxin peanut butter, the metabolism of aflatoxin contains aflatoxin M1 in the urine. In three urine samples of children who received aflatoxin B1 in 11.2-15.0 mg per day from peanut butter, the three samples were measured with aflatoxin M1.

Residue in aflatoxin

After the intake of aflatoxin, the aflatoxin in animals are mostly distributed in the liver, and the content in the liver can be 5-15 times than that of other organ tissues. The aflatoxin can also be detected in the kidney, spleen and adrenal glands. There is a very small amount of aflatoxin in the blood, which is generally not detected in the muscle. If not continuously ingesting aflatoxins, it generally does not accumulate in the body. Aflatoxins and their metabolites remain in the animal are excreted with milk, urine, feces, and respiration.

Experiments have shown that after aflatoxin B1 is taken in animals, aflatoxin B1 and its metabolites can be detected in liver, kidney, muscle, blood, milk, and eggs. This residue causes the contamination of animal food. Generally, about 1% of the aflatoxin B1 ingested by mammals is discharged into milk and urine in the form of M1. In the milk, it was found that Aflatoxin M1 was found in the milk after 11 hours of AFB intake, and the highest content was observed after 12-60 hours of AFB intake. Finally, Aflatoxin M1 decreases to a small amount after 5 days.

The Guangxi Health and Epidemic Prevention Station fed 12 dairy cows with different contents of AFB1 mixed in feed for 36 days to study the relationship of AFB1 transformation in cattle. The results showed that the residual amount of AFM1 in dairy cows with an average of 5.75% generally accounted for 3.45%-11.39% of the total intake of AFB1. Agacdelen (1993) reported that the laying hens were fed with AFB 1500μg/d, and the seventh day later AFB1 in 0.117 ppb was detected in the eggs. And the feeding of AFB1 was stopped for 4 days, and AFB1 was not detected in the eggs.

There is little information available on toxin residues in animal products for human consumption. In different countries, the maximum level of mandatory aflatoxin M1 is reported at 0.05-1 ppm, and aflatoxin B is 15PPb. The content of aflatoxin M1 and aflatoxin below this level are acceptable in most countries. The standard value for aflatoxins in Chinese foods is being formulated.

Look! Harm and Prevention in Aflatoxin.

Aflatoxin prevention measures

Anti-mildew means to prevent raw materials and products from being contaminated by mold and toxins. Preventing the production of molds produced toxin is the key to preventing AF. The main measures for anti-mildew are as follows.

1. Controlling moisture is to control the moisture and relative humidity of the storage environment in raw materials such as grains and feed.

(1) The strict control of the moisture in raw materials such as grains. The raw materials such as grains must be started anti-mildew when the grains are harvested in the field. The purpose is to make it dry quickly after harvesting, and make the content of moisture in the grain falls to a safe range in a short time. Generally, the content of moisture in grains is below 13%, the corn is below 12.5%, and the peanut kernel is below 8%. The mold in the grain is not easy to multiply in this range of content in moisture. The content of moisture in plant cakes, fish meal, meat, and bone meal should not exceed 12%.

(2) Strictly control the moisture of the feed. When the content of the moisture in the feed exceeds 15%, the mold can grow and multiply. When it reaches 17-18%, it is a suitable condition for fungal production. In China, the content of moisture in compound feed for pigs and chickens are no more than 14% in the north and no more than 12% in the south. And in the feed of concentrates for pig and chicken, it should be less than 12% in the north and less than 10% in the south. In general, the content of moisture in the pellets should be controlled at 12.5%, and it should be less than 12% in the powder.

(3) Strictly control the moisture in the process of production. It is to control the quality of the water vapor, the length of the conveying pipe, the temperature, and pressure of the regulator, the structure of the cooler and the cooling temperature during the processing of feed.

(4) Strictly control the relative humidity of storage in warehouses stored raw materials and finished product. The warehouse should be clean and dry before storage. The storage of bulk should have ventilation equipment. The external humidity in a closed warehouse should be controlled at the proper range not affecting the grain inside the warehouse.

2. Store grains at low temperatures. The ideal conditions of storage are to store the grain in a dry and low-temperature state. The temperature is below 12°C, which can effectively control the reproduction and production of mold. Raw materials and finished products with high moisture content should be stored at a lowe temperature. For example, if the moisture of rice is 12%, it can be stored at 35°C, and when the content of moisture is 14%, it should be stored within 20°C.

3. Reduce contamination and remove damaged grains. The damaged raw materials are easily contaminated by molds from the wounds. Therefore, you need to minimize damage in the seeds, avoid pests, groin, and abrasion, prevent surface damage of grains and peanuts and remove damaged kernels in harvest and storage.

4. Use the preservation method of carbon dioxide gas. Most molds are aerobic, and they cannot grow without oxygen. Therefore, the grain can be kept in the closed container filled with carbon dioxide gas for several months without mold. At the same time, this method also has a control effect on the pest. Silage can be prevented from spoilage by eliminating oxygen.

5. Apply anti-fungal agents promptly. Ingredients of feed and compound feed processed in wet and hot seasons are prone to mildew, and anti-mold agents can be used to extend their shelf life. Common antifungal agents are mainly propionic acid or propionate, sorbitol and potassium sorbate, sodium diacetate, fumaric acid and so on. Among them, propionic acid or propionate(sodium propionate, calcium propionate) are the most widely used. Besides, some anti-mold agents (such as sodium diacetate) can improve the utilization of feed and improve the palatability of feed. Silage additives (such as liquid ammonia, propionic acid, microbial culture, or enzymatic silage) are beneficial to prevent the production of mycotoxin.

6. Try to shorten the storage period. The ingredients of feed and feed should be used in the order according to the storage period, and it is better to use the feed with a short storage period firstly and use feed as soon as possible. The farm's self-mixed feed should not be kept more than three days to not be contaminated and propagated by mold for a long time.

7. Keep clean in the equipment contained mold spores from air and dust. Therefore, the warehouse and various production and transportation links should be kept in clean as much as possible.

8. Breed anti-infective or anti-toxigenic varieties of the crop. The anti-mildew ability of crops is related to genetic factors. Cultivate and select crop in varieties with resistance to infestation or anti-toxicity. This variety of crops can use their resistance and provides a simple and effective way to control the contamination of Aspergillus flavus and toxin.

9. Use radiation to prevent mildew. The use of radiation can not only prevent mildew but also improve the freshness of feed and food. The Institute for Atomic Energy of USDA used 1 × 106 Rad γ-rays to irradiate food and feed and stored it in a harsh environment at 30°C and relative humidity of 80% or more for 45 days. The result is that the food and feed are detected without mold.

Look! Harm and Prevention in Aflatoxin.

Detoxification measures in aflatoxin

After the feed has been contaminated with mold and mycotoxins, it should be managed to destroy and remove contaminated. The method is in the following points.

1. The method in the elimination of mildew is work. The distribution of aflatoxin-contaminated grains is very uneven, and most of them are damaged in insect-worm and discolored particles. If contaminated grains are removed, the level of toxin will be reduced. Check whether it is polluted or not in the feed and grain through visual and olfactory judgments, and discard the contaminated grains. The silage of ruminants should be carefully examined in the feeding, and mildew in it should be found and should be removed.

2. Radiation UV or γ-ray can effectively kill mold and destroy the chemical structure of aflatoxin to achieve the purpose of detoxification. With high-pressure mercury lamp with high-intensity irradiation, the rate of detoxification rate can reach 97-99%. Feng Dingyuan (1995) reported that aflatoxin B1 decreased by 42.31% and G1 and G2 were almost completely removed, after under natural exposure in the daylight for 30 hours in peanut cake.

3. Washing method can be used. Aflatoxin is insoluble in water and stable to heat. Aflatoxin is unevenly distributed in crops such as corn. The total amount of aflatoxin presenting in the epidermis is more than 80%. The washing method is utilized effectively. The specific gravity between the embryo and the milk embryo of the corn is different, and the embryo or epidermis will be float on the water surface after the pulverization of corn. And most of the toxins in corn can be removed by floating. Laboratory and application results show that the average rate of detoxification by the method can reach more than 80%. Most of the peanut kernels contaminated by AF are light in weight. The seeds floating in the water are mostly kernels polluted by AF. This method can remove 88% of contamination in kernels.

4. The adhesive method is also effective. The effectiveness of using a binder to agglomerating aflatoxin B1 in vitro has been confirmed. The main binders are hydrated sodium aluminosilicate (HSCAS), clay, zeolite, bentonite, activated carbon, montmorillonite, and an equivalent bonding agent. However, the binding effect of HSCAS in the body is the same as in vitro and the effection of the binder to aflatoxin is good. The minimum requirement for the binder is porosity and its the size of the pore is in the range of 0.015-0.090 mm (150 angstroms to 900 angstroms). Lindemann et al. (1993) reported that the addition of 0.25% or 0.5% bentonite sodium to a weaned piglet in the feed containing AFB1 at 800 μg/kg increased the average in daily gain and intake of feed in piglets.

5. Chemical drugs can be used in detoxification. Some chemical preparations such as hypochlorous acid, sodium hypochlorite, hydrogen peroxide, ammonia, and sodium hydroxide have certain effects on the removal of AF. Feng Dingyuan et al. (1997) reported that peanut cakes were treated with 0.25%, 0.50%, and 1.0% sodium hypochlorite respectively. The time in treatment was from 24, 48 to 72 hours. The difference in the result of detoxification between the groups was not significant, and the total reduction of aflatoxin was more than 93%, but the effect on aflatoxin is different and has the greatest reduction in aflatoxin B1. Ammonia treatment is to treat corn, soybean meal, peanut meal, etc. contaminated with aflatoxin, with ammonia or ammonia water. Under the effect of ammonia, the toxin lactone ring can be cracked to achieve the purpose of detoxification.

6. Biological detoxification method can be used. This method can remove certain microorganisms and use their biotransformation to destroy or convert mycotoxins into low-toxic substances. It has been reported that microorganisms such as a root-free enzyme, rice root enzyme, Aspergillus niger, and Bacillus subtilis have a good effect on removing aflatoxin.

7. Adding sulfur-containing amino acids to remove the toxin. Two kinds of sulfur-containing amino acids, included methionine and cysteine, are added to the feed. Under the effect of enzymes, the sulfur atoms can be used to promote the synthesis of glutathione (GSH), GSH, which is resistant to toxic substances in vitro. Hu Lan et al. (2001) reported that the feed of the broiler contained AF2mg.kg-1, and adding it with methionine 0.2 g.kg-1 and cysteine 0.4g.kg-1 respectively. The result is that it can maintain at the same level between red blood cells and white blood cells. An alanine aminotransferase (GPT) was increased, but the ratio was very small. It indicates that it would weaken the liver damage caused by AF in broilers.

8. The mixed dilution method is a choice. Raw materials and feeds can be diluted with raw materials and feeds of contamination in mold exceeding the specified value. But the dilution should be uniform, and after dilution, the mold should be prevented from growing again. You need to use the diluted feed immediately when it is made. This method applies to farms.

9. Have a try in adding vitamin C. Vitamin C blocks the epoxidation of aflatoxin B1 and prevents from oxidation to an active form of toxic substances. Adding a certain amount of vitamin C to the diet, together with the appropriate level of amino acids, is an effective way to avoid aflatoxin poisoning. Hu Shaoqi (2001) took an experiment that there are aflatoxin B1 and aflatoxin B1 + vitamin C group in a broiler, the former led to immune failure in infectious bursal disease.

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