Reproductive Performance of Mares Fed Dietary Zearalenone

Area of Science:

• Veterinary Medicine
• Animal Reproduction
• Toxicology

Background:

• Zearalenone (ZON) is an estrogenic mycotoxin with known reproductive effects in various species.
• Previous studies on ZON's impact on horse reproduction are conflicting and inconclusive, often due to co-exposure to other mycotoxins.
• Understanding ZON's specific effects on mare reproduction is crucial for equine health and management.

Purpose of the Study:

• To assess the effects of chronic zearalenone consumption on reproductive parameters in cycling mares.
• To evaluate ZON's impact on key reproductive hormones (estradiol and progesterone) and overall estrogenicity.
• To monitor reproductive physiology, pregnancy establishment, and early fetal development in mares exposed to ZON.

Main Methods:

• Cycling mares (n=7/group) were fed controlled diets with pure ZON (0, 2, or 8 mg/day) for three estrous cycles.
• Reproductive hormones (estradiol [E2], progesterone [P4]) and total estrogenicity were measured via RIA and E-screen assay.
• Reproductive status, uterine health, ovarian activity, and pregnancy were monitored using ultrasound and clinical assessments.

Main Results:

• No significant differences in estradiol (E2) or progesterone (P4) levels were observed between ZON-treated and control groups.
• A significant increase in P4 levels across cycles was noted in the high ZON (8 mg/day) group (P < 0.01).
• Pregnancy rates were variable, with fewer pregnancies and fetal heartbeats in the low ZON group compared to controls, while the high ZON group showed no adverse effects on pregnancy establishment.

Conclusions:

• Chronic ZON consumption at 2 or 8 mg/day did not demonstrate significant detrimental effects on mare reproductive hormones or physiology.
• While not definitively detrimental, the observed trends in progesterone and variable pregnancy rates suggest potential subtle impacts.
• The study highlights the need for larger sample sizes to overcome individual variability in assessing ZON's reproductive effects in mares and notes the absence of severe toxicological signs.