Influence of cervical dilatation on pregnancy rates and embryonic development in inseminated mares

摘要

Success rates of transcervical equine embryo transfer still vary widely. The possibility that hormonal changes due to cervical manipulation might contribute to this variation is still debated. Studies on the effects of cervical stimulation on hormone secretion and the estrous cycle have produced contradictory results; while insertion of aluminum rods into the cervix did not alter the estrous cycle [1], manual dilatation of the cervical canal was shown in some studies [24] to shorten diestrus. Moreover, PGF_(2#alpha# concentrations in uterine flushings obtained via the cervix were higher than in flushings collected at hysterectomy [5]. Transcervical uterine flushing for embryo collection can also result in prostaglandin release in embryo donor mares [6]. In potential recipient mares, however, placing an external sheath from an embryo transfer catheter into the cervix and the caudal part of the corpus uteri for 60 s did not cause any changes in hormone secretion and estrous cycle patterns [7] and sham transfers provoked either no [6] or only rare [8] measurable release of PGF2#alpha#. Also in cycling mares, cervical dilatation up to a diameter of 4 cm did not reveal any rises of plasma 13,14-dihydro-15-keto PGF2#alpha# (PGFM) but did shorten the estrous cycle, depending on the extent of cervical dilatation [9]. The aim of the present study was to investigate the effects of cervical dilatation on Day 7 after ovulation on pregnancy rate and early embryonic development in inseminated mares.