Zearalenone (ZEN) is a mycotoxin produced by Fusarium graminearum, F. culmorum, F. crookwellense, F. equiseti and F. semitectum. This mycotoxin regularly co-exists with deoxynivalenol (DON), as the same fungi (F. graminearum or F. culmorum) can produce both compounds. ZEN contamination in grains varies. According to the BIOMIN quarterly survey, there is a worldwide occurrence of ZEN at different levels and in different grains (Figures 1, 2 and 3).
The guidance levels for ZEN in animal feed, introduced by the European Commission, are 0.25 mg/kg in complementary and complete feeding stuffs for sows and fattening pigs, and 0.1 mg/kg in the same commodities for piglets and gilts. Once ZEN is ingested, part is transformed to its metabolites, α-zearalenol and β-zearalenol. In pigs, the main metabolite is α-zearalenol. The toxicity of this metabolite is four-fold higher, which explains the higher sensitivity of pigs to ZEN. The effects and intoxication of ZEN depends on the amount ingested, length of exposure, age and reproductive phase of the animal.
The main effect of ZEN is on reproduction, by blocking the normal synthesis of hormones. ZEN resembles the estradiol molecule and competes with it for estradiol receptors (estrogenic receptors). These receptors can be found in different organs such as the liver, kidneys, testis, prostate gland, hypothalamus gland, pituitary gland, ovaries and intestines.
This estrogenic effect disrupts the endocrine system, disturbing the hypothalamic-pituitary-ovarian axis and supressing follicle-stimulating hormone secretion in the ovaries.
ZEN effect in gilts
Due to their undeveloped endocrine system, gilts are even more sensitive to the estrogenic effects of ZEN. The results of ZEN ingestion are; hyperaemia and vulva swelling (hyperestrogenism), uterus mass increase, ovarian follicle atresia and atrophic ovaries, and vaginal or rectal prolapse.