[The effect of the covering of mares during the postpartum heat on the pregnancy rate].

The present study was carried out to investigate the pregnancy rate after covering in the foal heat (Group I), in the subsequent spontaneous heat (Group II), and in the induced heat (Group III) after administration of 7.5 mg of the prostaglandin F2 alpha analogue Luprostiol (Reprodin, Bayer) between the 20th and 22nd day post partum. Breeding during foal heat resulted in a pregnancy rate of 43.9% compared to 48.6% in the subsequent spontaneous heat post partum. Of 18 mares in group III, 14 mares had a foal heat, whereas 4 others had not shown a foal heat. 1-8 days after treatment, 14 mares (77.8%) returned to an oestrus. In consideration of the mares which had shown a foal heat, oestrus was induced in 85.7% of treated mares. In this group, a pregnancy rate of 50.0% was achieved. In conclusion, the results of the present study indicate that induction of oestrus by treatment with prostaglandin 20-22 days after parturition for covering is a good alternative.