1College of Agriculture, Razi University, Kermanshah, Iran
2Department of Animal Science, Iranian Research Organization Science and Technology, Tehran, Iran
Receive Date: 01 April 2012,
Revise Date: 28 April 2012,
Accept Date: 06 July 2012
Two experiments were performed to determine the effectiveness of different progestogens contained in intravaginal devices, different doses of eCG and subsequent hCG treatment on the reproductive performance of estrus-induced mature Lori ewes. In the first experiment, 88 ewes were allocated into two groups, and were treated with either fluorogestone acetate (FGA) sponges or Controlled Internal Drug Release devices (CIDR).The sponges were withdrawn 13 days after insertion and then ewes were treated with either 350 IU or 500 IU of eCG by intramuscular injection. There was no significant difference among treatments in the percentage of ewes in estrus or the interval to the onset of estrus. However, the conception rate and prolificacy of ewes treated with 350 IU eCG, in both the FGA and CIDR groups, was higher than ewes treated with 500 IU of eCG. In the second experiment 384 ewes were randomly divided into three groups and after synchronization with FGA spongesand 350 IU of eCG, 128 ewes in the first group (T1) were injected 250 IU hCG when artificially inseminated, 128 ewes in the second group (T2) were injected 250 IU hCG 12 days after AI and the 128 ewes in the third group (C) acted as the control group. Estrous was determined by monitoring 35 teaser rams to calculate estrous rate. Prolificacy and conception rate were assessed and serum progesterone (P4) concentrations were measured on days 12, 14 and 16 days after AI. Prolificacy was increased in the T1 group compared with control group (P<0.05) and conception rates were higher in hCG treatments (P<0.05). The weight of single lambs on the day ofbirth increased with the hCG injection on days 0 and 12 (P<0.05). The P4 concentration was higher in the hCG-treated groups compared with the control ewes on day 16 (P<0.05). It is concluded that CIDR and FGA sponges were equally effective for estrous induction in anestrous Lori ewes and P4 concentrations increased with 200 IU hCG given at the time of AI or 12 days after AI which could improve reproductive performance.
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