The Thai Journal of Veterinary Medicine


The present study was conducted to synchronize estrus and fixed time insemination in dairy cattle during the hot and humid months (July to November) in Thailand. Thirty-four cows and heifers were treated by using norgestomet+PGF2α+equine chorionic gonadotropin (eCG) program. Norgestomet was implanted subcutaneously at the back of the ear for 10 days. PGF2α was administered IM on day 8 and one injection of eCG was given on the day of implant removal. Fixed time artificial insemination(AI) were performed twice, at about 54-60 and 70-74 h, after the eCG injection. Blood samples were collected at 22 days after AI for progesterone (P4) assay. Real time B-mode ultrasonography was used to determine the pregnancy between 27-30 days after AI and then pregnancy was confirmed by rectal palpation between 60-90 days after AI. Of 34 cows, 16 cows (47%) had serum P4 higher than 1 ng/ml, while only 5 cows (15%) were positive for pregnancy detection using ultrasounography and rectal palpation. Cows with Body Condition Score (BCS) of 3 and non-repeat breeder cows tended to have a higher pregnancy rate than cows with BCS of 2.5 and repeat breeder cows. In conclusion, low pregnancy rate was found after using hormonal treatments during the hot and humid months in Thailand.

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