EXPERIENCES ON THE ALTRENOGEST TREATMENT OF NONPREGNANT BREEDING MARES IN HUNGARIAN STUDS DURING THE SPRING TRANSITION PERIOD

Effectiveness Of an orally active synthetic gestagen, altrenogest (Reg umate Equine, Roussel-Uclaf) was tested at the end of winter-season. T he oral treatments were carried out in 27 mares with a daily dose of 0 .044 mg/kg for 10 days. 24 mares served as untreated control. The auth ors tried to elicit the first ovulation, indicating the beginning of b reeding season in mares, non-pregnant at least for 180 days, showing e xpressed follicular activity at the beginning of the experiment (acycl ic animals, n = 34). In animals showing cyclic ovarian function at tha t time (n = 17), the authors tried to synchronize the sexual function. Acyclic and cyclic characters of the ovarian function were differenti ated by RIA-determination of progesterone (P4) level of blood (plasma) pairs collected with a 10-day interval. Efficacy of the treatment was qualified by following up the breeding data during 60 days, as well a s by means of P4-analyses carried out on every 3-4 days during a 35 da ys period (P4-profile; Figs 1, 2 and 3). Of the acyclic mares the altr enogest-treated animals were in heat, ovulated, and mated/inseminated earlier (P<0,0.1, Table 1, Table 2 furthermore P<0.02, respectively) a nd more of them conceived during the first weeks of breeding season (T able 4) than their untreated mates (n = 16). Following the treating-pe riod, 4 control (36%) and only 1 treated mares (7%) remained acyclic d uring 35 days. However, the treatments did not influence the incidence of luteal phases shorter than 10 days, as well as longer than 17-18 d ays (Table 3). Similar but less expressed tendencies were found for th e altrenogest-treated cyclic animals (n = 9, Table 5 and 6). According to the results obtained, the authors found the altrenogest treatment as a method capable of shortening the spring transition period.