Prostaglandins are widely used in herd management due to their luteolytic properties. They have also a direct effect on the myometrium. We hypothesized, that dissimilar prostaglandin preparations would differ as to their contractile effect. Intrauterine pressure was recorded during the diestrus of lactating dairy cows using a transcervically placed intraluminal pressure microtransducer. After recording physiologic uterine motility for 30 min, prostaglandins (dinoprost, DL-cloprostenol, D-cloprostenol) or a placebo 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 recording 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 DL-cloprostenol, while dinoprost yielded the steadiest plateau from this period until the end of the recording session. These results contrast with those of earlier studies comparing prostaglandins after intravenous administration.

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The objective of this study was to investigate the effects of cisapride (CIS), metoclopramide (MET) and bethanechol (BET) on contractility parameters from smooth muscle preparations of the abomasal antrum and proximal duodenum of cows. Smooth muscle preparations were harvested shortly post-mortem from 42 healthy dairy cows, and concentration-response curves were performed by cumulative application of the drugs. Cisapride and MET did not have any significant effect on the contractility parameters studied, while BET induced a significant, concentration-dependent increase in basal tone (BT), mean amplitude (Amean), and area under the curve (AUC) in smooth muscle preparations from the abomasal antrum, but not from the duodenum. The effect of BET on BT was more pronounced in specimens with longitudinal orientation while the maximal obtainable effect (Vm) in Amean was more pronounced in circular-oriented preparations. Atropine (1 x 10-5 m) significantly inhibited the effect of BET, whereas pre-incubation with hexamethonium or tetrodotoxin (TTX) had no effect, suggesting that the effect was mediated by cholinergic receptors on the smooth muscle. The results may be relevant to diseases or disorders associated with gastric emptying and gastric hypomotility. Further investigations are warranted to investigate the potential ability of BET to enhance abomasal emptying of adult dairy cows.

Background: Delayed uterine involution has negative effects on the fertility of cows; use of prostaglandin F2alpha alone as a single treatment has not been shown to consistently improve fertility. Combined administration of PGF2alpha and PGE2 increased uterine pressure in healthy cows. We hypothesized, that the combination of both prostaglandins would accelerate uterine involution and have, therefore, a positive effect on fertility variables. In commercial dairy farming, the benefit of a single post partum combined prostaglandin treatment should be demonstrated.

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