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Feeding Mycotoxins to Animals Increases the Mycotoxins Risk to Humans

07 April 2017

Nutriad

Mycotoxins are highly toxic secondary metabolic products of molds. Mycotoxin producing molds damage crops which can cause great economic losses at all levels of food and feed production.

Moreover, many of the mycotoxins impair health, cause diseases and death in humans and animals which consume contaminated food or feed products. At the moment, there are more than 400 known mycotoxins. Those of most concern can be divided into six major categories: aflatoxins, trichothecenes, fumonisins, zearalenone, ochratoxins, and ergot alkaloids.

Discovery of zearalenone

Zearalenone (ZEN) was discovered, identified, and named by two separate groups of investigators in the 1960s. Symptoms associated with ZEN in livestock feed were seen more than 50 years ago in 1963 (Christensen et al., 1965). In 1963, herds of young swine in Minnesota that consumed pelleted feeds were found to have symptoms which included: tumefaction of the vulva, prolapsed vagina, and hypertrophy of the mammary glands. The same feed was then fed to guinea pigs and white rats and both developed enlarged uteri. In 1964, a herd of swine that was fed grain (containing 30% mold ridden corn and 70% sound corn) developed similar symptoms. Christensen and colleagues were able to isolate compounds from the moldy corn, which were not isolated from the sound corn, identifying them as F-1 and F-2. F-1 was confirmed through various reactions to be ergosterol. F-2 was purified and identified (Christensen et al., 1963). Urry et al., (1966) identified the chemical structures of F-2, later naming it ZEN due to its structural name in combination with the name of the fungus it produces (Fusarium graminearum; teleomorph Gibberella zeae).

Zearalenone in human food chain

A synthetic form of the metabolite α-ZAL, called zeranol (Ralgro©), has been used as an anabolic agent for both sheep and cattle. This synthetic form, used as a growth promoter was patented in the United States by some of the researchers who originally gave “zearalenone” its name. In 1989, zeranol, was banned by the European Union (EU). It remains a Food and Drug Administration (FDA) approved growth promoter and there are currently no FDA regulations regarding ZEN in the United States.

A feasibility study examining the relationship between urinary mycoestrogens, breast development and menarche found measurable levels of ZEN and its associated metabolites in urine samples of 163 New Jersey girls, ages 9-10 years (Bandera et al., 2011). There was 78% detection of urinary free mycoestrogens, with ZEN having the highest level and a 55% detection rate, while zeranol had a 20% detection rate and lower levels. Levels were similar between seasons of recruitment. Six girls reported popcorn intake prior to the study day and had significantly higher levels of ZEN and total metabolites. Beef intake was also found to be associated with higher urinary ZEN. From a public health standpoint, ZEN is a mycoestrogen of concern due to its estrogenic activity. Despite the low concentrations of mycotoxin in foods (μg/kg), there can be adverse health outcomes and the chronic effects of long-term exposure are not fully understood. Established tolerable daily intake (TDI) for ZEN is 0,5 µg/kg-body weight/day, whereas its maximum limits in foods in the EU range from 20 to 350 µg/kg.

Zearalenone in swine

Zearalenone mainly causes estrogenic effects in pigs. In pregnant sows it increases the occurrence of abortions and stillbirths. In others, zearalenone contaminated feed induces swelling and reddening of vulva, false heats and false pregnancy. ZEN has also been found to be a possible teratogen, or a compound with the ability to alter the developing embryo and fetus (Koraichi et al., 2011).

Mycotoxin deactivator effective against zearalenone

The objective of the study was to evaluate the influence of ZEN and TOXY-NIL® PLUS; a mycotoxin deactivator on the status and functioning of the reproductive system of gilts at puberty (first oestrus) at 6 months of age. The experimental period lasted 2 months.

30 Large White gilts, 6-months of age were allotted to 3 groups:

Control: good quality compound feed (10 animals)
ZEN: feed contaminated with 660 ppb ZEN (10 animals)
ZEN + TOXY-NIL®PLUS: feed contaminated with 660 ppb ZEN with inclusion of TOXY-NIL® PLUS at 1.0 kg/t (10 animals)

Oestrus signs such as behavioural changes and genital redness were visually observed twice a day and standing reflex was measured 3 times a day. After the trial at 8 months of age, 5 gilts from each group were euthanized for evaluation of the reproduction system. The parameters measured included length of uterus, size of vagina vestibule and length of vagina, length of cervix, ovarian size, and volume.

Results

The gilts which were fed ZEN contaminated diet had a significantly prolonged oestrus time compared to the control group and the contaminated group with TOXY-NIL® PLUS included (Fig.1). The mycotoxin also extended standing heat; however this effect was fully reduced by TOXY-NIL® PLUS (Fig.2).

Inspection of the reproductive tract of gilts after euthanasia showed that 660 ppb ZEN had a significant effect on the uterus length, size of vagina vestibule and volume and weight of the ovaries (Table 1). These observations confirmed suboptimal development of the reproductive system in gilts which were showing clear oestrus signs and prolonged standing heat. When gilts consumed contaminated feed with simultaneous inclusion of TOXY-NIL® PLUS, the length of uterus and volume of ovaries were similar to the control gilts.

Table 1. Status and functionality of the reproductive system

This study confirmed that the growth rate is not normally affected by the presence of ZEN in feed. The average daily weight gain between the three groups was not statistically different (Fig. 3).

Conclusion

The results of this study in breeding gilts showed that there was a significant influence of estrogen-like mycotoxin ZEN at 660 ppb on the reproductive function (uterus and vagina development, volume and weight of ovaries and oestrus signs). The negative effects of ZEN on the reproductive function of gilts were effectively reduced by the inclusion of TOXY-NIL® PLUS at 1 kg/t in the feed.

The results of above mentioned study indicate that the use of effective mycotoxin control offers an opportunity to significantly improve animal health and performance. The application of specific feed additives (mycotoxin deactivators) which are able to help reduce the negative effects of different mycotoxins in swine is highly recommended. Recent NUTRIAD web application - MYCOMAN® informs the user about mycotoxin challenges and based on the challenge levels calculates the necessary and effective dosage of NUTRIAD mycotoxin deactivators product line. MYCOMAN is currently available for free online from Android Play Store (Google) and iOS (App store).

References

1. Bandera, E.V., et al., Urinary mycoestrogens, body size and breast development in New Jersey girls. Sci Total Environ, 2011. 409(24): p. 5221-7.
2. Christensen, C.M., G.H. Nelson, and C.J. Mirocha, Effect on the white rat uterus of a toxic substance isolated from Fusarium. Applied microbiology, 1965. 13(5): p. 653-659.
3. Koraichi, F., et al., Zearalenone exposure modulates the expression of ABC transporters and nuclear receptors in pregnant rats and fetal liver. Toxicology Letters, 2012. 211: p. 246-256.
4. Urry, W.H., et al., The structure of zearalenone. Tetrahedron Letters, 1966. 7(27): p. 3109-3114.

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