Nutzung einer terminorientierten Besamung beim Rind auf der Grundlage einer Prostaglandin – GnRH-Behandlung
Abstract. Title of the paper: Practical application of timed artificial insemination in cattle using a GnRH and Prostaglandin treatment
Three experiments were conducted to establish a regime of oestrous synchronization and artificial insemination at a predetermined time in dairy cattle. In experiment 1, dairy heifers (n = 43) were synchronized by administering PGF2α on day 5, 8, 11 or 14 and the LH surge was recorded. Release of the LH surge ranged from 57.0 ± 8.6 h to 76.3 ± 10.0 h depending upon the day of induced luteolysis. The release of LH was followed by ovulations. The day of PGF2α administration did not affect the interval from LH peak to ovulation. In experiment 2, heifers (n = 30) were synchronized on days 8, 11 or 14 of the oestrous cycle. Animals received an injection of GnRH 65 h after induction of luteolysis. Uniform intervals from PGF2α application to LH surge were observed in animals given PGF2α on day 11 and 14. Variation for this parameter decreased also in the group of animals where luteolysis was induced on day 8. There were no significant differences due to treatment in the mean interval from LH-peak to ovulation.
In experiment 3, fixed time insemination was tested on the basis of data from Experiments 1 and 2. Synchronized heifers and high yielding cows received GnRH 65 hours after PGF2α administererd between d 8 and 14 of the oestrous cycle. Artificial insemination was carried out 13 h after GnRH application. Pregnancy rates show, that fixed time artificial insemination, independent of the recorded onset of estrus can result in high pregnancy rates. Pregnancy rates in animals at different locations were higher after induction of ovulation and timed artificial insemination (79.0, 76.0 and 47.1, 53.3 %) than in control groups with insemination after detected estrus (69.8, 63.2 and 38.6, 45.0 %).