Effect of low-dose zearalenone exposure on luteal function, follicular activity and uterine oedema in cycling mares

The effect of 10-day zearalenone administration starting 10 days after ovul ation was studied in 6 cycling trotter mares in the summer period. After an entire oestrous cycle (Cycle 1), mares were given 7 mg purified zearalenon e per os daily (1 mg/ml in ethyl alcohol) beginning on Day 10 of Cycle 2. T oxin exposure was continued until the subsequent ovulation. Luteal function and follicular activity were monitored daily by rectal palpation, ultrason ography and blood sampling for progesterone. During toxin exposure, all ani mals were in good physical condition. The toxin had no effect on the length of the interovulatory intervals, luteal and follicular phases. It did not influence significantly the plasma progesterone profiles (logistic curve pa rameters A1 to A6), the follicular activity (growth rate, maximum size of t he ovulatory follicles, maximum number and the time of first increase in th e number of large follicles) and the uterine oedema. It is concluded that i n cyclic mares the methods used in this study could not detect any adverse effect of zearalenone (administered at a low dose similar to natural exposu re) on reproduction.