Effect of two dosages of d-cloprostenol on intrauterine pressure and uterine motility during dioestrus in experimental cows.

Prostaglandins are commonly used in herd management for their luteolytic properties; however, prostaglandins also have a direct contractile effect on the myometrium. We hypothesized that different dosages (0.15 and 0.3 mg) of d-cloprostenol, a synthetical prostaglandin F2 alpha preparation, would differ as to their contractile effects on the uterus. Intrauterine pressure was recorded during dioestrus of lactating dairy cows, using a transcervically placed intraluminal pressure microtransducer. After recording of physiological uterine motility for 30 min, a placebo or d-cloprostenol at one of the two different dosages was administered intramuscularly, followed by a 2-h recording period. Significant differences were found for the area under the curve (P < or = 0.05) and mean amplitude (P < or = 0.05), whereas the number of spikes per 15 min and the baseline pressure during the last 3 min of every 15-min period did not differ significantly among treatments. Peak values for area under the curve and mean amplitude were found between 15 and 30 min after administration of the lower dosage of d-cloprostenol, and between 75 and 90 min after administration of the higher dosage. Using the higher dosage of d-cloprostenol, a steady plateau from 15 to 30 min after administration until the end of the recording session was obtained. Thus, double the luteolytic dose of the d-cloprostenol preparation gives a significantly better reaction in terms of uterine contractility than the single dose.