Aflatoxins are toxigenic metabolites that are certainly happening by lethal strains of Aspergillus parasiticus and A. flavus that frequently dwell and colonize feed components and various nutritive foodstuffs in addition to principal crops such as corn, groundnuts, rice and maize 1516. The four major naturally produced aflatoxins in milk foodstuffs of dairy animals are known as G1, G2, B1 and B2 10. Where letter “B” talk about the blue fluorescent color whereas “G” substituted for green fluorescent that are formed on thin layer chromatography plates in Ultraviolet light, though the subscript numbers 1 & 2 specify main and small mixtures 1016. The occurrence of aflatoxin B1 (AFB1) in milk is usually after ingested, then secrete enzyme and hydroxylated in order to form aflatoxin M1 (AFM1) that is secreted and concealed in the milk and its product 1718. According to International Agency for Research on Cancer WHO, 19 aflatoxin B1 and aflatoxin M1 are categorized in type I cancer-causing agent. However, among both Aflatoxins (AFM1 and AFB1), aflatoxin B1 is the most serious one, since it is extremely oncogenic and producing liver cancer in humans in addition to its establishing power in most foods and feeds 20. Probably this indicates that different dairy foodstuffs may enclose contaminants that pose hazard to public health, predominantly for youngsters who devour the dairy products 16 Moreover, immunosuppression and growth impairment can be caused in both animals and humans through frequent acquaintance of aflatoxin 1821.

Aflatoxins are mainly caused by mycotoxins that introduced in milk and milk-based foodstuffs. The aflatoxin B1 is naturally occurring in feed by means of various metabolites including AFM1 that are hydroxylated copies of AFB1, through bio-transformation in mammary glands excreted in milk, which is causative agent for liver cancer 6. The principal sources of alfatoxin for cattle and human are frequent exposure and consumption of groundnuts and maize due to greater susceptibility and high degree of contamination of both feedstuffs for aflatoxin throughout the world 22. Also, Wu and Khlangwiset, 10 suggested that peanuts and Maize are the chief sources of dairy animal and human acquaintance to aflatoxin. For the reason that, existences of aflatoxin contaminated animal feeds can biologically be produces aflatoxin in milk. So this phenomenon is the most worrying delinquent through time in all over the world, as the most important cow milk is principally precious while feeding are contaminated everywhere in the world 23. As Nyaga, 24 reported, milk is highly contaminated with aflatoxins in and around Addis Ababa milk shed. Moreover, totally dairy cow feeds exceeded 5 mg/kg of AFB1 can be produce the over conventional standard perimeter of 0.05 mg/L aflatoxins in the milk. The result as well indicates that the major sources of aflatoxin in and around peri-urban areas of Addis Ababa dairy value chain is pollution of noug cake that is extensively used as dairy cattle feed AFB1.

According to Elzupir & Elhussein, 25 investigation of different feeds shown that brewer's waterless yeast, wheat bran and maize grain had comparatively low levels of aflatoxin contamination, however noug cakes maize and groundnuts are extremely contaminated with aflatoxin B1. Besides, dairy cows that have consumed aflatoxin B₁ contaminated feed are secreted aflatoxin M₁ in the milk 26. There was adequate and necessary association among AFB1 and AFM1, as presence of enormous amount of AFB1 in feed results in high contamination of milk by AFM1. After ingesting of AFB1 contaminated feeds, AFM1 is excreted within twelve hours of consumption 27. Additionally as Dawit et al. 28 founds, there was a reasonable link between level of AFB1contamination in feed ingested by animal and aflatoxin M₁ in milk. As authors found transference of aflatoxin from animal feeds to milk and milk products are within an average of approximately 1%.

Mycotoxin M1 and M2 is derivative of milk aflatoxins, that are heat impervious and hydroxylated metabolites created by lactating cow that were consuming feeds contaminated by aflatoxin 2629. As various authors indicated, the consumed AFB1 is metabolized into AFM1 while AFB2 is metabolized into AFM2 in dairy cattle, with assessed transformation percentage of 1-3 among AFB1 and AFM1 30.

Moreover, the most important metabolite that excreted by various animals in milk is aflatoxin M1 26. AFM1 is formed through bioconversion in mammary glands of dairy cattle by oxidative reactions catalyzed in liver CYP enzyme mechanism, which is principal to hydroxylation in the terminal furan ring of the parental molecule AFM1 represents the 95% of AFs detected in milk. Other metabolites, such as Q1 (AFQ1), aflatoxicol (AFL), M2 (AFM2), and M4 (AFM4) are distinguished in small quantities and then deliberated of less importance for human wellbeing.

Occurrences and Effects of Aflatoxin in Milk and its By-Products

Aflatoxin has critically various occurrences degree, effects, concentration and character depends on prevalent substrate, nature of mould and weather conditions 1026. Aspergillus parasiticus formulate whole aflatoxin type (AFG1, AFG2, AFB1 and AFB2) on corn whereas A. flavus produces primarily aflatoxin B1and B2 on corn. Among the feed used for milk production there are three main feedstuffs; peanuts, cottonseed and corn have great character to be attacked by Aspergillus species throughout growing, yield and loading or storing 10. Generally, colonization arises and assisted through storage especially in the case of small grains and soybean. The formation of Aflatoxin can be promoted by high moisture content, poor storage surroundings, kernel damage, temperature, nonexistence of ventilation 31. Moreover as the production of milk and milk based foodstuffs needs various processes, the impacts of handling and storage process has great potential on the dissemination and stability of Alfatoxin M1. Due to that relatively the occurrence of Alfatoxin in milk is higher when comparing with occurrence of Alfatoxin in the other milk products such as cheese, yogurt, butter, butter milk, cream, and skim milk because of some mechanical, chemical and biological processes are performed depending on the types of the products 32.

As many authors suggested incidence of aflatoxin in cheese may due to several potential reasons. The primary reason for occurrence AFM1 in the raw milk is the import of leftover of AFB1 from polluted feeds of animal to milk. The second one is production of AFB1, AFB2, AFG1, and AFG2 by molds that propagate on cheese although the minute amount of CHO does not create suitable environment and substrate. The 3^rd one is the consumptions cheese made from milk powder contaminated with aflatoxin M₁. However, several authors reported that increases in AFM1 concentration in cheese as a function of cheese variety machineries to be recycled to process it, and the quantity of water removed in the course of manufacture 17. As Barbiroli et al. 33 stated, particular influences can be occurred by high temperature, renneting, pH, and duration of pressing can exaggerated the volume of water removed and increase the amount of AFM1 in the cheese.

Aflatoxicosis is illness initiated by the feeding of the metabolites of mold (aflatoxins) that formed by certain species of Aspergillus parasitisus and Aspergillus flavus. Among all aflatoxin, AFB1 is a strong cancer mediator through raising the actual protein necessity of dairy cow.

In dairy animals, the harmfulness aflatoxins have an acute and chronic syndrome; also it shows relatively disparate properties on different individual animals based on vulnerability to aflatoxins. Effects aflatoxins on animal health are depend on age, species, nutrition, and sex as well as immunity status. In animals, acute toxicities caused by feeding of excessive amount of aflatoxins, whereas the chronic toxicities are initiated by ingesting of less quantity, this type of aflatoxicosis are the reason for liver impairment by cancer, GIT injury, reduction in desire for food, rate of reproduction, growth, production and body weight 18. As Denli & Pérez, 34 reported clinical signs of acute aflatoxicosis involves anorexia, depression, malady, loss of weight, bleeding from GIT, liver damage and pulmonary edema. As well decreased feed intake, milk production and growth rate are the principal symptom of chronic aflatoxin exterminating. Furthermore, lactating cow do not exposed to alfatoxin polluted feeds since it deteriorate the feature of milk and milk based products and even can cause death of lactating dairy cow may follow within 60 minutes/days mainly in acute aflatoxin toxicity 161834.

Presence Mycotoxins particularly AFM1in milk and dairy products can create severe health problems on human. As International Agency for Research on Cancer classification, AFB1 and AFM1 are classified as class 1 and 2B are possible carouses for human carcinogens, correspondingly 19. Consequently, as dairy products are extensively consumed by children and infants as well as adults, the occurrence of aflatoxins in in milk and milk products particularly their substantial entrances in milk based foodstuffs has a severe suffering on human wellbeing.

Generally the major effects of aflatoxin on human health are includes affects the nervous system (abnormal behavior and depression), reduced sperm count and increase infertility, low birth weight and reduces the rate of growth in infants and children. Consumption of con taminated milk with AFM1 particularly by the youngsters devastate their disease resistance mechanism and subsidize to poor growth because of in most countries youngsters are not consumed cow's milk and so there immunity is less competent at their infant stage 22. Moreover, according to WHO, 7 reported, possibly aflatoxin is accountable and play role in up to 30% of the cases of liver cancer internationally in every year. Subsequently as human affected by aflatoxins, liver cancer is followed in addition to manifesting of jaundice eye sclera.

Figure 1, Figure 2

Currently, the acceptablelevels of aflatoxins in milk and milk based products are different based on various factors. Reasons like economic status of the countries and meteorological situations are the most influencing factors in permitting levels of aflatoxin 32. Several countries are certified and set the acceptable levels of aflatoxins in milk and milk products to reduce and control harmful properties of the aflatoxin. For instance in US, Food and Drug Administration (FDA) has allowed overall quantity of 0 .5 g/kg or 50 ng/l in milk and 20 ng/g in dairy cattle feed 35. In Europe, the acceptable amount is 0.005 mg/kg AFM1 in milk foodstuffs of dairy cattle provided for young children 36. Moreover, the determined levels of AFM1 in milk and milk based products in different regions of the world are demonstrated in (table 1, table 2)

Food safety problems generate massive problem on the country’s budget such as expenditures to outbreak surveys and food recalls, national supervisions from enlarged therapeutic payments, absenteeism from work and school due to food born disease, loss of consumer confidence in the foodstuffs, improved burdens on previously imposed and unwell subsidized healthcare structures 37.

Moreover along with economic loss and financial expenditures to public health, farmer and livestock husbandry manufacturing, fatalities attributable to aflatoxin pollution of foods involves expenditures to treatment of food intoxication and medication cost. As per Boutrif 37 reports, yearly, around 20% of the foods manufactured in the world are infected by mycotoxins; of which aflatoxins have a superior portion compared to others. Occurrence of dairy cattle infection and cancer, decrease in milk production and productivity as well as declining of immune system in dairy cows are particular illustrations of charges to milk based foodstuffs as well as dairy cattle production. Bearing in mind such like enormous economic damages and public health safety, inhibition and frustration of the aflatoxin in food products of animal origin and dairy cow feed is critical 38.

Aflatoxicosis or contamination of milk based products by aflatoxin can only be prevented by feeding aflatoxin free rations to dairy animal which can be enhanced through preventing fungal growth in feed and good agricultural practice in dairy production farm and processing scheme. So preventing contamination of aflatoxin needs continues plus systematic scrutiny and analysis platform 39.

Generally, to reduce the threat of animal and human exposure to aflatoxins requires multidisciplinary and universal methodology due to the complex nature of aflatoxin contamination ways of milk and milk products. For that reason, it requires increasing of public perception on aflatoxins and applying scrutiny provision beside the whole dairy products. Commonly, elimination of aflatoxin requires both direct and indirect reduction approaches of aflatoxin in milk and dairy cow feed 36.

Using of aflatoxins polluted feed for dairy cattle are typically leads to the production of contaminated milk with aflatoxins. Hence, indirect controlling of dairy cattle feed hygiene is potential in decreasing aflatoxin contamination 3940. Strictly decreasing means of aflatoxin contamination in the course of crop production, traditional and industrial storage of livestock feed as well as livestock feed factories are obligatory to attain the objective, value and wellbeing concerns 40. Furthermore, effective ways of decreasing the contamination can be gained through proper storing of crops which embraces keeping crops on dry and clean sides, keeping crops from wetness, high temperature, pests and practice of fungicidal drugs 10. Additional central way of regulatory and decreasing aflatoxin pollution is strict observation of hygienic conditions in conventional and modern levels factories and livestock feed storerooms 40. Monitoring growth of fungus and formation of aflatoxin in old-style farms and storages are extremely imperative 3839. Level aflatoxin in milk can also be influenced by seasonal situation, for instance occurrences of aflatoxin is greater in winter and autumn compared to summer and spring due to inaccessibility of fresh feeds and farmers use warehoused forages in this unfavorable time of year 3136. So, it is indispensable to advance improper storeroom and moisture conditions of livestock feed storage.

To achieve effective prevention and control of aflatoxins, persistent and vigilant observation of diverse techniques of production and storage condition, controlling moisture content and adjustment of heat through ventilation methods, use of uncontaminated materials aided for preparing livestock feed are compulsory 41. In order to avoid mold development and inhibit growth of the molds in the early occurrences of contamination, microbes, chemicals, ionizing rays and absorbent material can be used 42. According to Dakovic´ et al. 43 indication, outstanding approach of decreasing aflatoxin contamination in infected animal feed is using of aflatoxin absorbents. In the course of using absorbents, aflatoxins existing in animal feed prevents from toxic reactions in livestock body as well as from absorption into digestive tract by binding to absorbents Huwig et al. 44.

In addition, prevention of aflatoxins by chemical compounds involves series organic acids like sorbic, propionic, acetic acids and benzoic, organic acid slats such as potassium sorbate, calcium propionate, liquid or solid copper sulfate as well as diverse microbes such as lactobacillus brevis and lactobacillus pentose’s is alternative approach of decreasing aflatoxin in animals feed 45.

The use of biological methods, chemical and contaminant absorbents are also helpful for direct reduction of aflatoxin in milk and its product 46. Using of toxin absorbents is one of the chief direct methods of decreasing amount of aflatoxin in milk as absorbent top soil such as vermiculite; bentonite, active carbon and hydrated sodium calcium aluminosilicate (HSCAS) have been recognized as absorbent complexes for captivating different contaminants in aqueous atmospheres 17.

Besides, hydrogen peroxide is the most effective chemical compounds reduced aflatoxin and used for storing of milk based foodstuffs 47. Application of combined chemicals such as lactoperoxidase, riboflavin and hydrogen peroxide in addition to heat treatment is better to attain sufficient outcomes in reducing aflatoxin in milk. Also, use of potassium sulfite for neutralizing AFM1 in milk is well known 4647.

Biological means of reducing aflatoxin is easiest and cheap approach and so it is interesting than other method. Currently, various investigations are conducted on detecting active microbes 46. For instance, as Line et al., 48 indicated in their research, gram negative bacterium which is known as Flavobacterium aurantiacum, has been used for decreasing production of aflatoxin in milk. This microbe has special ability, as it converts toxic ingredients of aflatoxin that exist in milk to harmless ingredients.

AFB1: Aflatoxin B1; AFB2: Aflatoxin B2; AFG1: Aflatoxin G1; AFG2: Aflatoxin G2; AFM1: Aflatoxin M1; EC: European Commission; EFSA: European Food Safety Authority; EFTA: European Free Trade Association; EU: European Union; FAO: Food And Agriculture Organization Of The United Nations; FAPAS: Food Analysis Performance Assessment Scheme; HSCAS: Hydrated Sodium Calcium Alumino Silicate; ILRI: International Livestock Research Institute; WHO: World Health Organization