Caspian Journal of Veterinary Sciences

Caspian Journal of Veterinary Sciences

Effect of progesterone-based synchronization protocols with (high cost) or without (low cost) GnRH and gonadotropins early in the breeding season on the fertility of Sanjabee ewe lambs

Articles in Press

Document Type : Original Article

Authors
Saeed Gholami 1
Mojtaba Goli 2
Hadi Cheraghi 3
1 DVM-graduated student, Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran.
2 Department of Clinical Science, Faculty of Veterinary Medicine, Razi University, Kermanshsh, Iran.
3 Department of Clinical Science, Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran.
10.22034/cjvs.2026.581905.1066
Abstract
Effect of a progesterone (P4)-based synchronization protocol with or without gonadotropins early in the breeding season on the fertility of Sanjabee ewe lambs was investigated. Forty-nine lambs aged 8-9 months received an intravaginal P4 releasing device (day -14) and allocated randomly to five groups: P4 Only, no further treatment; P4PG received PGF2α at device removal (day 0); P4GnRH received GnRH (day -14) and PGF2α (day 0); P4eCG and P4hCG groups were treated as P4GnRH plus eCG or hCG (day 0), respectively. At day 0, the ewes were introduced to five fertile rams for 7 days. Blood samples were collected on days -14, -1, 2, and 20 for P4 assay. Progesterone concentrations above one ng/ml on day 20 were considered as pregnancy. Pregnancy status on days 35 and 55 was performed by transrectal ultrasonography. There was no statistically significant difference in embryonic loss on day 35, or in pregnancy rates on days 35 and 55 among the groups. Loss of pregnancy on day 55 was only documented in P4GnRH (33.3%). Lambing and fertility rates were greatest in P4eCG (70.0%) and lowest in P4GnRH (22.2). The highest and lowest prolificacy were observed in P4eCG (1.14) and P4GnRH (0.67), respectively. Progesterone concentrations differed within the groups at days -14 and 2 with those at days -1 and 20 (p ≤ 0.05). In conclusion, adding gonadotropins to a 14-day P4-based synchronization program early in the breeding season resulted in no significant improvement in reproductive performance of Sanjabee ewe lambs.
Keywords
CIDR
ewe lambs
Sanjabee sheep
Subjects
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Caspian Journal of Veterinary Sciences

Articles in Press, Accepted Manuscript
Available Online from 09 November 2026

  • Receive Date 16 May 2026
  • Revise Date 23 June 2026
  • Accept Date 24 June 2026