**2.1. Aflatoxins**

The majority of microfungi are saprobiotic organisms that can be seen in all-natural media – earth, water, air. In nature, fungi can grow and invade any type of food, at any moment, if the conditions favorable for their growth are created. The latter are in general represented by: substrate humidity higher than 11.5%, relative humidity of the air of over 70%, oxygen presence of 1–2%, temperatures between 5 and 40°C, substratum pH of 4–8, aw between 0.7 and 0.85, relatively low light intensity and plant stress under the action of unfavorable medium

The direct action of fungi over live organisms is of tissular destructive levels and can be limited or generalized, determining diseases named mycoses. In the pathology of ruminants, the following types of fungi are generally involved: *Absidia, Alternaria, Aspergillus, Candida, Cryptococcus, Fusarium, Mucor, Penicillium, Rhizopus, Rhodotorula, Sporothrix, Stachybotrys, Trichoderma, Trichophyton, Trichosporon*. Of these, there are certain types which are recognized as having mycotoxigen potential: *Aspergillus, Fusarium, Penicillium, Mucor* and *Rhizopus*. According to FAO/IAEA, mycotoxines are secondary metabolites of fungi, non-volatile, organic, developed

The optimal temperature and humidity for developing a species of fungi does not correspond to the optimal parameters mentioned to produce mycotoxins, which determines a disparity between the presence of a species of fungi and the mycotoxins developed at that moment in the respective substrate. Note that there can be situations in which we find in analyzed food or fodder either only fungi, fungi and the mycotoxin/mycotoxins they produce or only mycotoxins. Mycotoxins are developed through a secondary metabolic process, which differs to the primary metabolism through its random nature, the diversity of compounds developed and the specificity of the thalli involved. The metabolic chains involved in the production of mycotoxins respond to the signals received by the fungus from

The diseases resulting from the activity of mycotoxins are named mycotoxicoses. The acute forms have a rapid evolution and are produced due to the action of high doses of mycotoxin over an organism. The chronicle forms, much more common, imply a slow development of the infection. In general, ruminants, compared to monogastric animals, are considered resistant to the action of most mycotoxins, attitude explained by the detoxifying role of ruminal microsymbionts and especially protozoa. Ruminal and intestinal microorganisms do not significantly degrade mycotoxins when the ruminant's food is rich in concentrated fodder, as an example, or when the quantity of mycotoxins ingested reaches over certain limits. Equally, rumen metabolites of the parent mycotoxins can become, after ruminal biodegradation, not just less toxic but, in some cases, also more aggressive than the initial substance. Even so, the clinical examination performed on the dairy cows from the studied farm did not reveal the presence of any symptom characteristic to mycoses or to mycotoxicoses at dairy cows. From this perspective, it is extremely useful the analysis of the quality of fodder in regards to their contamination with fungi and/or mycotoxins

Mycotoxins are secondary metabolites developed under increased temperature, humidity, aw, pH and their presence in fodder cannot be detected organoleptically. Furthermore, the

factors (action of damaging insects, climate factors etc.).

86 Ruminants - The Husbandry, Economic and Health Aspects

the outside medium, thus not being related to cellular growth.

and the application of preventive measures for the health of the animals.

**2. Mycotoxin occurrence and mycotoxicosis**

by fungi in both food and fodder [3].

Aflatoxins (AF) are mycotoxines produces in nature by fungi species of the *Aspergillus (A. flavus* and *A. parasiticus*) and more rarely *Penicillium* (*P. puberulum*, *P. citrinum, P. variable* and *Rhizopus* types. The notion of aflatoxin in common languages refers to all its four representative forms: AFB1 (C17H12O6 ), AFB2 (C17H14O6 ), AFG1 (C17H12O7 ) and AFG2 (C17H14O6 ). *A. flavus* produces AFG1 , AFG2 as well as AFB<sup>1</sup> and AFB<sup>2</sup> . Aflatoxins B2 and G2 are dehydrogenated derivatives of AFB<sup>1</sup> and AFB<sup>2</sup> . From a mycologic point of view there is a large quantitative and qualitative difference regarding the ability of the different fungi species of producing these mycotoxins, about half of the *A. flavus* species producing aflatoxins [4].

The AF group comprises around 20 mycotoxins (e.g. M1 , M<sup>2</sup> , B2a, AFL, AFL-M1 , P<sup>1</sup> , Q<sup>1</sup> , H1 etc.). The M1 and M<sup>2</sup> metabolites are hydroxylated derivatives of aflatoxins B1 and B<sup>2</sup> secreted in the animal milk following the consumption by the cows of food that has been contaminated with these [5].

At present, the kinetics of the transformations and the risk associated with the consumption and absorption of aflatoxins is well known, both at animals and at humans. The main conjugation way of aflatoxins is glucurono-conjugation, the resulting complex being eliminated through the bile. The liver is considered the target organ for aflatoxins. At this level, the metabolization of mycotoxins takes place under the action of microsomal enzymes. The reaction products are eliminated from the organism through excretion products (feces and urine) and milk in unmodified form as well as metabolites.

Moreover, *in vivo* studies showed the presence of AFM1

after 8 days in urine and after 9 days in feces [14].

The degradation of aflatoxins (AFB1

mycotoxin and nutritional state [16].

*2.1.1. Aflatoxins and milk production*

At dairy cows, the absorption of AFB1

For preventing the risk of transmitting AFB1

The transformation of AFB1

of hydroxylation. AFM1

istration of AFB<sup>1</sup>

aflatoxin.

in the milk is:

less toxic [15].

AFB<sup>1</sup>

to the conclusion that AFM1

in the ruminal content, which leads

Dairy Cows Health Risk: Mycotoxins http://dx.doi.org/10.5772/intechopen.72709

) in the rumen is relatively reduced,

in milk is realized following a process

, AFQ<sup>1</sup>

to the milk, the superior limit for the content of

/kg [21].

in the digestive tract is rapid and complete, which

which rep-

89

and AFB<sup>2</sup>

[9]. Although

in the food of

and aflatoxicol [17].

from public health

, with an average of 1.7%

and the quantity found

from fodder to milk has been

produced in the liver can reach the rumen, through the rumeno-

hepatic way [13]. At dairy cows, from the total of 4.52% aflatoxins detected in the organism,

resented 0.35% of the administered dose. At the sheep in lactation, from the 8.1% compared to the ingested dose, it was detected 6.4% in urine, 1.63% in feces and 0.1% in milk. After a period of 6 days from the administration, the aflatoxin was not detected anymore in milk,

, AFG1

with a proportion of under 10% at a quantity of ingested mycotoxin of 1–10 μg/ml which is

 is considered the most carcinogenic natural substance being recognized as the most aggressive mycotoxin, for all the animal species, including human. The carcinogenicity of aflatoxins is dependent upon: animal species, age, dosage ingested, duration of ingesting the

, AFG2

are metabolites (hydroxylated forms) of AFB1

1.55% was detected in urine, 2.79% in feces and 0.18% in milk, in the form of AFM1

, AFB<sup>2</sup>

from fodder in AFM<sup>1</sup>

explains its almost immediate transfer in the milk, under the shape of AFM1

[18, 19]. Other studies have reached the conclusion that certain quantities of AFB1

dairy cows (13 mg impure AF/day, over 7 days) can induce the decrease in production, with-

variable, with values comprised between 0.3 and 2.2% [20]. Milk production and body weight returned to normal limits within the next 5–8 days from removing the contaminated fodder.

this mycotoxin in the fodder of dairy cows with a production of 20 kg milk/day, after ingest-

It was administered to a lot of lactating cows, in their food ration, corn contaminated with 120 μg AF/kg fodder. As a result, it was discovered the apparition of reproductive disorders, health problems, as well as the decrease in milk production. After removing the contaminated

Diaz et al. [9] affirm that AF appear in milk after approximately 12 hours from the oral admin-

, the maximum quantity being registered after 24 hours from ingesting the

many researchers have concentrated their attention on the study of AFM1

reasons, its production represents between 1 and 3% of ingested AFB1

ing 6 kg of contaminated fodder/day has been evaluated at 5 μg AFB1

corn from the ration, the milk production rose to 28% within 3 weeks [22].

The mathematical relationship between the ingested quantity of AFB1

out the evident clinical sign of disease. The transfer rate of AFB1

and AFM<sup>2</sup>

found in milk. Other metabolites identified in cow milk are: AFM4

The studies regarding the distribution and metabolism of AFB1 marked with C14, in the organism of some animals, have demonstrated both the elimination in significant quantities of the mycotoxin from the organism in the first 24 hours, as well as the accumulation of the residual quantity in different organs (muscles, stomach, liver, heart etc.), accumulation conditioned by the dosage of mycotoxin ingested.

Naturally, ruminants seem to be more resistant to the action of aflatoxins compared to other species of animals, although the clinical signs of aflatoxicosis have been observed in cows, such as: the reduction in the ingestion of food, the decrease in the production of milk, the affliction of the hepatic function. The chronic exposure to the ingestion of aflatoxin determines an inefficient feeding, depression of the immune system and the reduction of the reproductive function [6].

The lipophilic mycotoxins with a small molecular mass like AFB1 are absorbed in the digestive tract through passive diffusion. Aflatoxins, like other mycotoxins, induce severe hepatic dysfunction confirmed through biochemical tests in numerous studies [7, 8].

The pathologic modifications are more alarming in dairy cows, with high production, which are more sensitive to toxins. AFB1 is a strong inhibitor of the protein synthesis which blocks *in vivo* the replication and transcription of DNA and inhibits the synthesis of RNA and proteins. The metabolic products of aflatoxin act on the chromatin inhibiting the transcription of genes and RNA polymerase, which as a result produces a decrease in the concentration of RNA and protein synthesis. *In vitro*, AFB<sup>1</sup> effectively couples with the DNA and causes irreversible mutations, which explains its incredibly strong carcinogenic effect. Approximately 90% of AFB1 is present in blood, in plasma, being linked especially to albumins. Aflatoxins are oxidized in the liver with formation of very reactive molecules, capable of binding the nucleic acids or functional proteins. This hepatic bioactivation has a considerable importance for animal health due to the active metabolites that form *in situ*, at tissue level. The metabolization of aflatoxins at hepatic level takes place under the action of the microsomal enzymes, the most active of these being P450.

After the oral administration of AFB1 , the metabolites are quickly found in urine and milk, while small quantities can be distinguished in feces which confirms the rapid absorption of AFB<sup>1</sup> in the digestive tract and hepatic metabolism [9].

In general, the ruminal degradability of AFB1 is minor and the toxicity of the metabolic products is similar to that of the parent molecule. Aflatoxins affect the ruminal function through the reduction of ruminal motility, the capacity of digesting celluloses, of producing volatile fat acids and proteolysis [10].

The ruminal juice and, moreover, the bacteria population from the cow and sheep rumen does not have the capacity to convert aflatoxins in other metabolites except for AFM1 which is found in large quantities in milk [11]. Auerbach et al. have observed that adding 9.5 ng AFB<sup>1</sup> /ml ruminal liquid did not alter *in vitro* the digestion of alfalfa and did not influence the production of volatile fat acids while, in another study, adding a dose of 1 μg AFB1 /ml highlighted the lowering of the ruminal capacity of producing the acids [12].

Moreover, *in vivo* studies showed the presence of AFM1 in the ruminal content, which leads to the conclusion that AFM1 produced in the liver can reach the rumen, through the rumenohepatic way [13]. At dairy cows, from the total of 4.52% aflatoxins detected in the organism, 1.55% was detected in urine, 2.79% in feces and 0.18% in milk, in the form of AFM1 which represented 0.35% of the administered dose. At the sheep in lactation, from the 8.1% compared to the ingested dose, it was detected 6.4% in urine, 1.63% in feces and 0.1% in milk. After a period of 6 days from the administration, the aflatoxin was not detected anymore in milk, after 8 days in urine and after 9 days in feces [14].

The degradation of aflatoxins (AFB1 , AFB<sup>2</sup> , AFG1 , AFG2 ) in the rumen is relatively reduced, with a proportion of under 10% at a quantity of ingested mycotoxin of 1–10 μg/ml which is less toxic [15].

AFB<sup>1</sup> is considered the most carcinogenic natural substance being recognized as the most aggressive mycotoxin, for all the animal species, including human. The carcinogenicity of aflatoxins is dependent upon: animal species, age, dosage ingested, duration of ingesting the mycotoxin and nutritional state [16].
