| Abstract: | Forty-eight crossbred Chianina cows (3 to 5 years of age), with an expected gestation length of 288 days, were randomly divided into four treatment groups to evaluate the use of dimenhydrinate (an antihistamine agent) in conjunction with dexamethasone (DEX) for inducing parturition in beef cattle. Group (A) received a 20 mg dose of DEX (im) on day 282 of gestation and a carrier vehicle (iv) 24 hours later (day 283); Group (B) was given a carrier vehicle (im) on day 282 and 500 mg of dimenhy-drinate (DMH) diluted in 200 ml of 2.5% dextrose-0.9% saline solution given (iv) on day 283 and Group (C) received 20 mg of DEX (im) on day 282 and 500 mg of DMH in solution (iv) on day 283 of gestation. The remaining 12 cows assigned to Group (D) were not handled and were allowed to calve under natural conditions. The number of cows calving and percent calving within 60 hours after the first injection were: 10(91%), none(0%) and 12(100%) for the DEX, DMH and DEX plus DMH groups, respectively. The mean gestation length of the control cows in Group (D) was 288.6 days. Frequency of dystocia was: 18.2, 8.3, 0 and 0% and retained placentae (>/=24 hours) was: 72.8, 16.6, 33.3 and 0% for DEX, DMH, DEX plus DMH and control groups, respectively. In this study, a 20 mg dose of DEX (im) followed 24 hours later with 500 mg of DMH (iv) was more successful for calving induction than when DEX or DMH was used alone. The combination DEX and DMH treatment induced calving in a shorter interval from treatment (P<.05) and decreased the incidence of retained placentae (P<.01) when compared with those induced following DEX treatment. |
