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The objective of this study was to compare reproductive performance parameters for two protocols for estrus synchronization in dairy heifers in Germany.
In the CIDR group (n=93) all heifers received a controlled intravaginal progesterone releasing insert (Eazi-Breed™ CIDR®; Pfizer Pharma GmbH; containing 1,38g of progesterone) on day 0. On day 7 these cows were given prostaglandin F2α (PGF2α) analogue cloprostenol (Estrumate®, Intervet Deutschland GmbH, 0.5mg per animal i.m.), and the CIDR® insert was removed. Any mucus attached to the insert was scored on a 4-point scale: 0=no mucus; 1=clear; 2=bloody; 3=yellow/cloudy mucus. In the PG group (n=98) all heifers were given PGF2α analogue cloprostenol on day 7. Between day 8 and 11 heat detection was conducted twice daily for 30 minutes. All heifers in estrus were bred by artificial insemination (AI) and pregnancy was diagnosed 40 days after AI by transrectal palpation.
In the CIDR group the 4-day-service rate was 91.4%, in the PG group 70.4% (p<0.05). More heifers in the CIDR group were pregnant than in the PGF2α protocol (76.3 vs. 56.1%,p<0.05). Mucus scores of 2 and 3 indicative of vaginal irritation were observed in 91.9% of the CIDR group but did not affect the pregnancy outcome (OR = 0.652, CI95 =0.235-1.810; p=0.411).
In conclusion, the CIDR protocol improved reproductive parameters of dairy heifers compared with a PGF2α protocol. Mucus after removal of the CIDR® insert did not affect pregnancy rates.