The Effect of GnRH Administration on The Serum LH Response and Ovulation in The Early Postpartum Period of Dairy Cows


Abstract: The aims of this study were to determine whether GnRH would induce ovulation in dairy cows and to detect the acute changes in the serum luteinizing hormone (LH) after GnRH administration on day 14 postpartum. Ten holstein cows were divided into two groups: group I (n=6) and group II (Control, n=4). The six cows in group I received intramuscularly 0.5 mg gonadarelin and the four cows in group II were given intramuscularly 5 ml saline on day 14 postpartum. Ovarian activity and the size of the previously gravid uterine horn were monitored by rectal palpation and by the measurement of serum progesterone levels. The acute LH release in response to GnRH administration was evaluated from blood samples collected at 0 and 1,2,3,4,5 and 6 hours after injection. In group I, it was observed that the LH levels peaked within 2 h (from average 0.47 ng/ml to 24.66 ng/ml) and had returned to preinjection concentrations at 6 h (decreased to 0.59 ng/ml). In group II, serum LH levels were unchanged for 6 h after saline treatment. In group II, the first postpartum ovulation was observed on day 23 postpartum, while it was observed on day 15 postpartum in group I. As a result, it was concluded that GnRH treatment on day 14 postpartum has an adequate stimulative effect on LH release to start an ovulation response in healty dairy cows.

Keywords: GnRH, LH, Early Postpartum, Dairy cows

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