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The objective of this study was to test the efficacy of a progesterone
releasing device (CIDR®, 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® 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® on d 20 p. i. (CIDR®
group) while group 2 (n = 38) remained untreated (control group).
CIDR® 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®, 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® 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® 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®, 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.
Clinical relevance: Supplementation with progesterone at d 20 p. i.
does not decrease early embryonic losses between d 27 and 39 p. i. or
increase the number of cows pregnant on d 39 p. i.