Replacement of the first GnRH administration in the Ovsynch protocol by selecting cows according to the stage of follicular development
2006
Hartman, P.(Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Klinika Chorob Prezvykavcu) | Zajic, J.(Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Klinika Chorob Prezvykavcu) | Cech, S.(Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Klinika Chorob Prezvykavcu) | Jan, Z.(Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Klinika Chorob Prezvykavcu) | Dolezel, R.(Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Klinika Chorob Prezvykavcu) E-mail:[email protected]
The first application of GnRH in the Ovsynch protocol was replaced by selecting the cows bearing corpus luteum as well as follicles in a defined stage of development at the moment of PGF2alpha administartion. In addition, various terms of GnRH administration after PGF2alpha application were tested. Seventy-five non-pregnant cows were divided into groups according to the phase of follicular development on D0 (day of PGF2alpha administration) - growth (GR, follicles 3.0-7.9 mm in diameter), early dominance (ED, dominant follicle 8.0-14.9 mm) and late dominance (LD, dominant follicle 15.0-23.0 mm). In addition, the cows were divided into groups according to the terms of GnRH administration (24, 48 or 72 h after PGF2alpha). In this way, groups GR 48, GR 72, ED 24, ED 48, ED 72, LD 24, LD 48 and LD 72 were established. The highest level of synchronization of ovulation (100% on D 3) as well as conception rate (50%) was achieved in group ED 48. This protocol gives an opportunity of timing artificial insemination to 18-24 hours after GnRH administration as ovulation occurs with a high probability within 24-48 hours after GnRH administration.
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