Induction of Parturition in the Cow using Cloprostenol and Dexamethasone in Combination.

Two experiments were designed to test the hypothesis that induction of parturition in the cow would be more predictable with the simultaneous use of a combination of cloprostenol and dexamethasone than with either hormone used alone.In experiment I all 19 beef cows treated with 500 mug cloprostenol and 25 mg dexamethasone in combination calved within 72 hours whereas dexamethasone (n = 19) or cloprostenol (n = 16) treatments alone each resulted in two induction failures. In those cows successfully induced, the mean interval from treatment to birth was 34.6 +/- 1.4 hours for the cloprostenol plus dexamethasone group, 43.3 +/- 2.4 hours for the dexamethasone group and 44.9 +/- 2.1 hours for the cloprostenol group. Control cows (n = 15) did not calve during the first 72 hours after treatment with saline. The incidence of retained placenta ranged from 19 to 53% in induced groups whereas placentae were not retained by cows in the control group.In experiment II all 30 beef cows in the cloprostenol plus dexamethasone group calved within the 72 hour limit, with a mean interval of 39.1 +/- 1.0 hours. Twenty-six of 31 cows calved within 72 hours with a mean interval of 51.9 +/- 3.4 hours after a single injection of cloprostenol and 29 of 33 cows calved within 72 hours with a mean interval of 52.6 +/- 3.3 hours after two injections of cloprostenol, 12 hours apart. Five of 34 control cows calved within 72 hours of time of treatment. The incidence of retained placenta was again high in induced cows. Results indicate that the simultaneous administration of cloprostenol and dexamethasone does constitute a safe, reliable and effective method of inducing parturition in the cow.