Efficacy of progesterone inserts (CIDR) to reduce early embryonic losses in dairy cows

The objective of this study was to test the efficacy of a progesterone releasing device (CIDR (R), Pfizer, Germany) inserted on day (d) 20 post insemination (p. i.) to reduce embryonic losses between d 27 and 39 p. i. Furthermore, we hypothesized that CIDR (R) increases blood progesterone levels during the application period, but does not affect the maintenance of pregnancy after removal. Material and methods: The study was conducted on a commercial dairy farm, randomly allocating 74 Holstein Friesian cows to one of two groups. These cows were nonpregnant after previous artificial insemination and treated with an Ovsynch protocol. Group 1 (n = 36) received a CIDR (R) on d 20 p. i. (CIDR (R) group) while group 2 (n = 38) remained untreated (control group). CIDR (R) was removed on d 39 p. i. Blood samples were drawn from all cows on d 20, 27, 39 and 55 p. i. for analysis of progesterone (P4) concentrations by immunoassay (ADVIA Centaur (R), Siemens, Germany). Pregnancy diagnosis was conducted on d 27 p. i. with ultrasonography, and on d 39 and 55 p. i. by transrectal palpation. Results: The overall prevalence rate of early embryonic losses between d 27 and 39 p. i. was 37.1% (CIDR (R) group 35.3%, control group 38.9%; p = 0.83). On d 39 p. i. 30.5% of all cows were pregnant and the percentage of pregnant cows did not differ between the study groups (p = 0.83). Progesterone levels on d 20 p. i. did not differ among cows which were pregnant on d 39 p. i. (p = 0.57). On d 27 p. i. progesterone levels in pregnant cows were higher in the CIDR (R) group (16.2 +/- 9.9 ng/ml) compared to the control group (11.2 +/- 3.4 ng/ml; p = 0.04). Progesterone concentrations were lower on d 39 p. i., but still differed between study groups (p = 0.05). After removal of CIDR (R), blood progesterone levels did not differ between pregnant cows of both study groups on d 55 p. i. (p = 0.36). Conclusion: The application of a progesterone releasing device led to increased blood progesterone levels during the application period, but did not affect maintenance of pregnancy after its removal.