Ovarian consequences of low dose peroral Fusarium (T-2) toxin in a ewe andheifer model

The effect of low dose peroral Fusarium produced T-2 toxin intake upon the ovarian function was evaluated in ewes (n = 30; Trial 1) and heifers (n = 7 ; Trial 2). Half of the ewes and all of the heifers were fed rich, acidosis -inducing concentrate. The 30 ewes were divided into 6 groups of 5 animals each. They were given 0, 0.3 or 0.9 mg/day (0, 5 or 15 mu g/kg) purified T- 2 toxin per os for 21 days (3x2 factorial design). Four of the 7 heifers we re fed 9 mg/day (25 ug/kg) of the same purified T-2 toxin for 20 days while 3 remained untreated. The estrus cycles in all animals were synchronized p rior to the trials and the T-2 exposure was started in the mid-luteal phase . The acidic condition in the rumen was estimated by the determination of u rinary net acid-base excretion. The ovarian activity was followed with bloo d sampling for progesterone on alternate days (Trial 1) or with ultrasonogr aphy and sampling for progesterone daily (Trial 2). All of the heifers and concentrate-fed ewes showed a compensated acidosis, during first two thirds of T-2 exposure. In Trial 1, ovarian malfunction manifested as lower P4 pe ak concentration in the midluteal phase, shortening of the CL lifespan and prolonged follicular phases. These malfunctions were detected in 3 and 3 ew es fed concentrate and 0.3 mg and 0.9 mg T-2 toxin. Lower P4 peak concentra tion was observed in 1 ewe fed regular diet and 0.9 mg T-2 toxin. None of t he control and acidotic groups (0 mg T-2), or ewes fed regular diet with 0. 3 mg T-2 showed any ovarian malfunction. In Trial 2, after PGF(2 alpha) adm inistration the ovulation occured later and the plasma progesterone level r emained low (< 3 nmol/l) for a longer period in T-2 treated heifers, than t heir untreated control mates (5.0 +/- 0.7 vs 3.7 +/- 0.5 d, P<0.05 and 8.3 +/- 0.4 vs 6.3 +/- 0.9 d, P<0.01, respectively). These results show that th e peroral T-2 intake can significantly retard the folliculus maturation and ovulation and perhaps the subsequent luteinisation also in ruminants kept on concentrate-rich diet. (C) 2000 by Elsevier Science Inc.