Reproductive Tract Changes in Pigs Related to Zearalenone
Reproductive failure is the most common cause of sacrificing sows from production herds. These failures can affect individual pigs, but they can also be a farm problem. Any region of the pig’s genital tract may be involved, with the uterus and ovaries being the most frequently affected organs. It is known that numerous microorganisms and toxins might cause genital problems in sows. Although reproductive problems are considered multifactorial, recognition of genital pathology is crucial as the first step in the diagnosis of reproductive disorders.
Mycotoxins affect sow reproduction
Mycotoxins are produced and excreted by fungi that grow in grains such as corn, wheat, sorghum and others. They can be formed before harvest, during storage or even worse in feeders. The most serious problem is the poisonings that occur gradually where pigs ingest small amounts of the toxin but for a prolonged period of time. These affect the health of animals and this is manifested in a decrease in their growth rate and their productive and reproductive efficiency.
Two mycotoxins are known to have effects on the reproductive system; zearalenone and ergot. Zearalenone (ZEA) is produced by Fusarium species. ZEA and its metabolites, α- and β-zearalenol are mycoestrogens that can interfere with estrogen signaling. Swine is the most sensitive animal species to zearalenone (Hagler et al., 2001). In swine, α-zearalenol is produced in large quantities increasing the uterotrophic activity.
Clinical and pathology effects
The examination of lesions in macroscopic form could help in the detection of any possible intoxication with mycotoxins such as zearalenone. Zearalenone is estrogenic and targets the urogenital system. Hyperestrogenism in female swine may be manifested as swelling of the vulva (Fig. 1) and enlargement of the mammary glands, especially in gilts. Dietary concentrations of 1 ppm zearalenone or more may produce hyperestrogenism in pigs (Kurtz and Mirocha, 1978). Zearalenone has been associated with feminization in young male swine, including testicular atrophy, swollen prepuce, and mammary gland enlargement (gynecomastia) (Fig. 2). In severe cases it is possible to observe rectal and vaginal prolapse (Fig. 3). Other effects related to higher concentrations include anestrus, nymphomania and pseudopregnancy. High concentrations of zearalenone (50 to 100ppm) in swine diets have been reported to adversely affect cycling, conception, ovulation and implantation. Placental membrane and fetal development also may be disrupted, resulting in decreased litter size and diminished viability of neonates (Chang et al., 1979; Miller et al., 1973; Sundloff and Strickland 1986). Zearalenone causes embryonic death, abortion (Fig. 4), inhibition of fetal development, and decreased numbers of fetuses present in exposed swine.
Piglets from sows receiving zearalenone may have enlarged external genitalia and uteri. Zearalenone and its metabolites, α- and β-zearalenol, are present in milk of exposed sows and may contribute to estrogenic effects in piglets (Palyusik et al., 1980; Dacasto et al., 1995) (Fig. 5). An increased incidence in splay leg and trembling piglets has been reported (Fig. 6). Lesions of hyperestrogenism including enlargement of the ovary and uterus (hydrometra) (Fig. 7), ovarian cysts, glandular proliferation of the endometrium, and epithelial proliferation in the vagina (Vanyi et al., 1994).
Mycotoxins can severely affect sow reproduction. It’s important to consider the presence of mycotoxins when no response to any kind of treatment is observed in case of reproductive problems in pigs. The use of an effective mycotoxin binder (Myco-ad / Vitafix) with proven in vivo protection of the target organs is recommended to protect animals from the negative effects of mycotoxins. Pathology offers a valuable tool for differential diagnosis and evaluation of the effectiveness of any mycotoxin binder being used.
Written by Margarita Trujano