Objective: To study the effect of CIDR on oestrous synchronization and comparison of twining percentage by using eCG and handing diet and their interaction.
Design: Completely randomized design.
Statistical analysis: Use of SPSS statistical program for parameter data and x2 and Man- Witny test for non- parameter data. Animals: A total of 69 ewes and 6 rams of Zandi breed.
Procedure: Sixty-nine Zandi ewes within 2-5 years old and weighting 47.9 (±5.6) Kg, were divided into 3 groups (group 1 fed in the pasture and two other groups were fed in their pens). In order to synchronize oestrous cycle, all ewes (in 3 groups) were treated for 13 days with a controlled internal drug-releasing device (CIDR). On the following day after removing CIDRs, ewes in groups 1 and 2 received an injection of 400 IU eCG. Two Zandi rams were then introduced to each group.
Results: The results of the present study indicated that oestrus was induced within 36-48h post CIDR withdrawal in 100, 87 and 96 percentage of ewes in groups 1,2 and 3 respectively and this differences were not significant. The percentage of parturition was 91, 83 and 87 in groups 1, 2 and 3 respectively and differences were not significant. The percentage of twining (based on ewes lambing) was significantly (P<0.05) lower in the group 3, comparing to groups I and 2 (29, 37 and 15 in groups 1,2 and 3 respectively). Male and single born lambs was heavier than female and twinborn lambs (4.2, 4.2 and 3.7, 3.5 respectively), but differences were not significant. However, these differences within each group were significant (P<0.05). The effect weight of dam on the born weight was also significant (P<0.05).
Conclusion: The result of this study indicated that using of synthetic hormone caused length period of parturition decreased. Also difference of age and weight of lambs are lower. Besides cueing the synthetic hormones caused that percentage of twining increased
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