Effect of CIDR, eCG and artificial insemination on conception rate and lambing rate in Zell ewes

Use of different estrus synchronization protocols and artificial insemination methods made variations in fecundity of Iranian Zell ewes. The purpose of the present study was to investigate pregnancy and lambing rates in Zell breed ewes following diverse progesterone treatment durations, eCG treatment doses and artificial insemination by transvaginal and/or laparoscopy methods. 180 cyclic, multiparous Iranian Zell ewes 45.5±2.5kg, were used in this experiment. The ewes were allocated randomly to 3 different groups (n = 60). Estrus was synchronized using CIDR for 10 (A group), 12 (B group) and 14 (C group) days. At CIDR removal time, the ewes in each group was assigned into 3 subgroups (n = 20 and received eCG (0, 400 and 500 IU), respectively. 54 hours after CIDR removal, the ewes in each subgroup was randomly divided into 2 equal groups (n=10) and inseminated by transvaginal and laparoscopy, respectively. While combination of eCG treatment and CIDR removal increased pregnancy rate in all groups, the number of estrus have been augmented only in A and B groups. The artificial insemination by laparoscopy method made higher pregnancy and lambing rate compared to transvaginal technique. 500 IU eCG administration simultaneous with CIDR removal and artificial insemination by laparoscopy exhibited the best performance for pregnancy and lambing rate in Iranian Zell ewes.