Fertirelin and buserelin compared by LH release, milk progesterone and subsequent reproductive performance in dairy cows treated for follicular cysts.

This field study compared the efficacy of a single injection of 200 microg fertirelin with that of 20 microg buserelin in shortening the recovery period of 68 laotating Holstein-Friesian cows with ovarian follicular cysts 65 d post partum or later. Differential diagnosis was based not only on palpation per rectum but also on skim milk progesterone profiles (<or= 1.0 ng/ml) spanning a 15-d period rather than the conventional 7-d period, and diagnostic accuracy was markedly enhanced by the 15-d progesterone profiles. At 2 to 2.5 h post treatment all the cows showed an LH increase four-fold or greater. Luteinization, indicated by progesterone levels (>or= 1.0 ng/ml) 1 wk after treatment, was evidenced in 75% of the fertirelin group and 72% of the buserelin group. A 74% conception rate was achieved in fertirelin-treated cows, with a mean interval of 71 d from treatment to conception. In the buserelin-treated cows, 65% conceived and the treatment-to-conception interval was 63 d. Differences were insignificant. At the doses used the two GnRH analogs were deemed equally effective in managing particularly stubborn follicular cysts.