Relationships between the conception rate of estrus synchronization using estradiol benzoate and CIDR (progesterone) and other parameters in Holstein lactating dairy cows

The purpose of this study was to determine the relationships between conception rate and other parameters before estrus synchronization with a Controlled Internal Drug Release Device (CIDR) and estradiol benzoate (EB). In the estrus synchronization program, animals were injected with 2 mg EB and then received a CIDR. Seven days later, the CIDR was removed and the animals were given an injection of Prostaglandin Fsub(2alpha). Twenty-four hours later, they received an injection of 1 mg EB, and they were artificially inseminated 24 h after that. This program was applied to 258 Holstein cows in Tohoku-machi (Aomori, Japan). Blood was collected at the beginning of the program, and the conception rate was determined about 40 days after insemination. The relationships among conception rate, blood biochemical values, age, body condition score and days in milk were statistically analyzed to determine better conditions for cow conception. The conception rate of the cows in the high progesterone group (more than 1 ng/ml, Psub(4)+) was significantly higher than that of the low progesterone group (less than 1 ng/ml, Psub(4)-; 47.9% vs. 28.6% P0.01). In the Psub(4)- groups, the serum phospholipid level was significantly higher in the conception group than in the nonconception group, and the same tendency was seen in the Psub(4)+ groups. Blood urea nitrogen (BUN), albumin (Alb), and total cholesterol (TChol) were significantly higher in the conception group compared with the non-conception group, but no with Psub(4) was observed. We concluded that 1) the conception rate of the Psub(4)-group was remarkably low, that 2) the low conception rate and low Psub(4) level was related to a low PL level and that 3) BUN, Alb and TChol were higher in the conception group, although no relation with Psub(4) was found.