Five-day protocols of estrus synchronization with new or reused CIDR and different eCG doses in ewes

ABSTRACT The objective of this study was to compare reproductive performance and progesterone (P4) concentration in serum of synchronized ewes with new and reused (up to five times) CIDR in five-day protocols. Two experiments were conducted in the reproductive season, in two consecutive years. In experiment 1: 125 µg of PGF2α and 200 IU of eCG were applied at removal of the CIDR: CIDR1-200 (new intravaginal devices, control), CIDR2-200, CIDR3-200, CIDR4-200, and CIDR5-200 (groups with CIDR from second to fifth use, respectively). In experiment 2, ewes received the same protocol with a dose of 400 IU eCG: CIDR1-400 (control), CIDR2-400, CIDR3-400, CIDR4-400, and CIDR5-400 (groups with CIDR from second to fifth use, respectively). In the first experiment, estrus rate was 92% in the first and second uses, 100% in the third and fourth uses, and 95% in the fifth use. Pregnancy rates were 85% in first and second uses and 81, 73, and 57% from third to fifth CIDR uses, respectively. In the second experiment, estrus rate was 100, 96, 92, 96, and 95% from the first to fifth uses, respectively. Pregnancy rates were 85, 88, 85, 77, and 62% from the first to fifth uses, respectively. Estrus and pregnancy rates did not differ statistically. Estrus was concentrated between 24 to 48 h in experiment 1 and between 24 to 36 h in experiment 2. Prolificacy index was 1.3 and 1.6 in the first and second experiments, respectively. Progesterone concentration was >2 ng/mL after the insertion of CIDR in all groups. The CIDR (plus PGF2α and eCG) can be used up to four times for estrus synchronization in five-day protocols without affecting reproductive performance.