**2.3. Zearalenone**

Zearalenone (ZEA) is a mycotoxin produced by fungi species of the *Fusarium* (*F. graminearum, F. tricictum*) and is most commonly found in cereal grain.

From a chemical point of view, zearalenone (C18H22O5 ) is a lactone of the resorcilic acid, with a structure similar to steroid hormones [5].

An experimental study followed the administration of 385–1925 ppb ZEA during 7 weeks din not show a change in milk production, nor the presence of ZEA residues in milk, serum, urine or tissue. Both ZEA and its metabolites are absorbed at intestinal level, covering the enterohepatic cycle [40].

α and β-zearalenol are derivatives of ZEA that are eliminated from the organism through feces and urine and, to a lower degree, through milk. From these, α-zearalenol is considered the metabolite with the strongest estrogenic activity. Another metabolite of ZEA, which only develops in reduced quantities in animals, is zeranol, substance with a strong anabolic effect [41].

## *2.3.1. Toxic effects at ruminants*

The symptoms of ZEA toxicosis are: uterus hypertropia, swelling of the vulva and mammary glands, decline in the ovulation rate and disturbance of the heat cycle, conception rate is low at dairy cows, the estrogen effect of ZEA being owed to the link of the mycotoxin to the cytoplasmic estrogen receptor.

**2.4. Trichothecene**

link in positions 9 and 10 [5].

Trichothecenes are a group of 43 mycotoxins (DON or vomitoxin, NIV, DAS, T-2 toxin etc.) with a similar chemical structure, developed by species of fungi from the following types: *Fusarium* (*F. graminearum*, *F. sporotrichioides*, *F. culmorum, F. poae*), *Myrothecium sp., Phomopsis* 

Dairy Cows Health Risk: Mycotoxins http://dx.doi.org/10.5772/intechopen.72709 95

From a chemical point of view, trichothecenes are derivative compounds of a tetracyclic sesquiterpene nucleus containing the epoxy- stable group in positions 12 and 13 and double C-C

Trichothecenes are metabolized *in vivo* in four ways: hydrolysis at the ester group level, hydroxylation, epoxy reduction and conjugation in the digestive tract, liver and other target organs of the animal organism [46]. The metabolization of trichothecenes is relatively simple, the halving time in the plasma varying between several minutes and several hours, depending on the mycotoxin. Within 24 hours of the oral administration, in the digestive tract of bovines were found both parental compounds and their metabolites, free and glucorono-conjugated [47].

In general, the DON, T-2 toxin and DAS mycotoxins do not accumulate in significant quantities in the organism, regardless of the administration method, since their metabolic compounds are eliminated from the organism within days. In certain situations though, there can be accumulations of the lipophilic trichothecenes, T-2 toxin and DAS, at the skin and fat tissue level. *In vitro* incubation in ruminal fluid of the DON mycotoxin, for 48 hours, determined its

Charmley et al. administered a ration of contaminated wheat and corn to 18 primiparous cows, formulated in order to induce a daily consumption of 0.59 mg, 42 mg and 104 mg DON. The authors saw that an increased concentration of DON in the ration did not affect fodder consumption or milk production. There were however modifications of the fat percentage in the milk and of the fat production, for the cows that received 42 mg of toxin daily.

Ruminal microsymbionts can degrade DON resulting in the formation of 12,13-de-epoxideoxinivalenol (DOM-1). Côté et al. ascertained, following the administration of a ration with 66 mg DON/kg fodder, the presence of the DOM-1 metabolite in amount of 30 μg/l in milk and the absence of the parental mycotoxin [49]. In a study on lactating sheep, Prelusky et al. administered 880 mg DON/kg fodder, for 3 days and highlighted the presence in the milk of

In a study done in North Carolina, Whitlow et al. found a significant decrease in the production of milk at cows that consumed concentrated fodder contaminated with 0.8 mg DON/kg DM. Such a result can be explained through the synergic effect of mycotoxins associated with DON even though these were not identified. The presence of DON residue in the animal tis-

As is the case for other mycotoxins, studies regarding the adding of DON to fodder din not reveal the same toxicity compared to the food naturally contaminated with DON [51]. This is explicable due to the multiple interactions between mycotoxins in fodder, under natural

partial conversion into deepoxy-DON, metabolite non-toxic for ruminants.

The authors did not observe the transfer of DON or deepoxy-DON in milk [48].

220 μg/l mycotoxin, of which the majority was DOM-1 [44].

sue was not identified in this study [50].

conditions.

*sp., Stachybotrys sp., Trichoderma sp.* and *Trichothecium sp.* [23].

It was discovered that the milk production decreased, infertility and hypoestrogenism appeared in the case of cows that consumed fodder contaminated with ZEA or with other fungi of the *Fusarium* type. Coppock et al. have shown that the effects of ZEA over the reproductive apparatus (vaginitis, vaginal secretions, mammary gland enlargement) at dairy cows can be strengthened through the synergic action of 600 ppb ZEA and 440 ppb DON in food; the consumption of food decreases which leads to the reduction of milk production, cases of diarrhea, increased infections of the reproductive tract and the entire reproductive activity is compromised. In general, it is considered that 400 ppb ZEA in the food is the maximum concentration for which the reproductive activity of dairy cows is not affected [42].

A secretory activity of the mammary gland was observed at heifers that consumed fungi contaminated corn in the pre-puberty period. The administration during three estral cycles, at a heifer lot, of 250 mg purified ZEA, determined the reduction of the conception rate with 62% while at the control lot, the rate of conception was reduced by 87% [43].

Signs of hyperestrogenism were shown in cows that consumed fodder contaminated with 1 mg ZEA/kg fodder, over 5 days, while at sheep that received small doses of up to 24 mg ZEA/day/animal administered through fodder during the same period did not produce any evident clinical effects over them, after the breeding period [42].

#### *2.3.2. Transmission of zearalenone to milk of dairy cows*

In general, it is considered that the transfer of ZEA and its metabolites in milk is very low [44].

Many researchers associate the reduced milk production, low fertility and hyperestrogenism at cows with the presence of ZEA in cereal or hay. Shreeve et al. ascertained that dairy cows fed with a ration containing 385–1982 μg ZEA/kg fodder, over 7 weeks, had a normal production of milk and there were no cases mycotoxin residues in milk, urine, serum or tissue [45]. In a 2004 study regarding the contamination with aflatoxin, ochratoxin and zearalenone, wheat and barley bran samples which were administered as a supplement to the food of dairy cows were analyzed. At the same time, determinations were done regarding the mycotoxin transfer in blood, milk and urine for the cows that consumed the contaminated feed. The results obtained showed the absence of aflatoxins AB1 , AB<sup>2</sup> , AG1 and AG2 , as well as the absence of ZEA (values under 5 ppb in fodder and under 1 ppb in serum, milk and urine) in the fodder samples analyzed (values under the detection limit of 0.1 ppb). In a significant proportion, of approximately 90%, ZEA is transformed in α-zearalenone whose toxicity is very high and, in a smaller proportion, in β-zearalenol. As in the case of OTA, protozoa are 9 times more active than bacteria in the degrading of ZEA [23]. The transformation at ruminal level of ZEA in zearalenol, together with the reduction in polarity, affects the absorption and excretion rate of the toxin thus, [23] in accordance with many other studies, reducing the elimination rate of ZEA and its metabolites in milk.
