Dinoprost Versus Cloprostenol

Does Route of Injection Modulate their Efficacy in Dairy Cattle?

Abstract

This factorial study was conducted to determine the reproductive performance of402 dairy cattle treated with either dinoprost (25 mg) or cloprostenol (500 pg), intravenously (IV) or intramuscularly (IM), for synchronization of estrus in a randomized clinical trial. Breeding, conception and pregnancy rates were analyzed with multivariate logistic regression. The model included the treatments (2 types of prostaglandins and 2 routes of injection) as well as eight clinically-relevant covariables. Interactions between treatments were not significant and comparisons were made on the main effect. Comparisons between types of prostaglandins (PGF2a) showed similar breeding rates (82.6 vs 83.0%; P=0.93), but lower conception rate (38.6 vs 46.6%; P=0.13) and pregnancy rate (31.4 vs 39.2%; P=0.14) for dinoprost versus cloprostenol. When comparing routes of injection, a similar breeding rate (84.1 vs 81.4%; P=0.45), but lower conception rate (38.7 vs 46.7%; P=0.13) and pregnancy rate (32.5 vs 38.1%; P=0.23) were noted for IM versus IV injections. The statistical power of the study was 19%, which allowed detection (P<0.05) of a 5% difference or more in pregnancy rate between the main effect of treatments (200 animals per sample).
Gender of calves was recorded on 117 calves and analyzed with univariate logistic regression. Overall, the male calf rate was not different from the expected population value (57.3 vs 53.0%; P=0.36). There was a greater proportion of male calves when using dinoprost compared to cloprostenol (72.3 vs 47.1%; P<0.01), when using IV rather than IM injections (66.1 vs 49.2%; P=0.07) and when inseminating cattle 4 days or later after PGF2 injection instead of earlier (69.4 vs 51.9%; P=0.08). It is concluded that the type of PGF2a used and the route of injection might affect conception rate and hence, pregnancy rate, and that the statistical power of the study was too weak to detect any significant differences. It is also concluded that the interval (days) from PGF2a injection to breeding, the type of PGF2a and the route of injection might influence the sex ratio of calves.