Estrous response to synchronization of estrus using different progesterone treatments outside the natural breeding season in ewes

Atrialwas conducted to investigate the efficiency of synchronization using different progesterone treatments outside the natural breeding season. Ninety multiparous Karakul ewes were randomly assigned to one of three treatment groups (n = 30/group). In the progesterone treated group, ewes were injected intramuscularly (i.m.) with 20 mg progesterone acetate in oil every second day for 12 days, plus an i.m. injection of 500 IU eCG on day 12. The CIDR treated group, the animals were treated with the intravaginal devices impregnated with 0.3 g of progesterone for 12 days and injected i.m. with 500 IU eCG at withdrawal while in the third group, the ewes were treated with MAP sponges impregnated with 60 mg medroxyprogesterone acetate (MAP) for 12 days and injected i.m. with 500 IU eCG at sponge withdrawal. The interval from the cessation of treatment to the onset of estrus was significantly (p < 0.05) longer in the progesterone in oil group, compared to CIDR and MAP sponge groups (51.4±10, 30.1±7.6 and 29.6±5.6 h, respectively). The estrous response for the sponge and device groups was higher, compared to the group injected with progesterone (93.3% for CIDR, 100% for MAP sponge and 80% for the oil treated group). The duration of the induced estrous period did not differ significantly between the treatment groups. The results of the present study show that estrous synchronization with CIDR and MAP sponge followed by an i.m. administration of eCG is superior under local conditions for fixed time AI in Karakul ewes outside the natural breeding season. © 2005 Elsevier B.V. All rights reserved.