Comparing CIDR with progesterone injections and eCG with human recombinant FSH for synchronizing estrous cycle in ewes.

Background: It is desirable in estrus synchronization in sheep to avoid intravaginal devices and to shorten the program from 14 to 6 days. Moreover, replacement of eCG with safe, cheap, and efficient gonadotropin is in worldwide demand.

Aims: This study investigates the possibility of replacing eCG with human recombinant FSH (hrFSH) and CIDR with progesterone injections for estrous synchronization in ewes.

Methods: Assaf and Lacaune ewes (n=170) were divided into two groups and synchronized with either progesterone injections for 6 days or CIDR for 14 days. Ewes assigned in the injection group, received progesterone (37.5 mg; SC) and GnRH analogue (7.5 µg Alarelin acetate; IM) on day 0 of the experiment. On days 3 and 6, ewes received 25 and 12.5 mg progesterone (SC), respectively. On day 6, ewes in both groups received prostaglandin F₂α (250 µg Cloprostenol; IM), and were divided into two subgroups to receive either hrFSH (75 IU Follitropin alfa; SC) or eCG (400 IU; IM). On day 7, fertile rams were introduced to ewes for 21 days. Data were analyzed using GLM and Glimmix.

Results: There was no difference in the respective lambing rates, prolificacy, and fecundity between CIDR (71.1, 1.63, and 1.16%) and injections (66.7, 1.55, and 1.03%); between eCG (71.4, 1.60, and 1.14%), and hrFSH (66.3, 1.58, and 1.05%, P>0.05).

Conclusion: In conclusion, 6-day progesterone injection-based protocol produced similar results to 14-day CIDR program and hrFSH could be an effective alternative for eCG during estrus synchronization in ewes.