The Thai Journal of Veterinary Medicine


In general, artificial insemination (AI) in sheep using frozen-thawed (FT) semen in commercial scale islimited due to the fact that the FT semen of sheep needs to be deposited into the uterus to achieve an acceptablefertility rate. Laparoscopic insemination with FT semen gives commercially acceptable fertility rates, however it is noteconomical and animal friendly. An alternative method is trans-cervical AI (TCAI). However, the unusual anatomy ofthe sheep cervix is a major limitation to this technique. In ewe, the cervical lumen has a convoluted and tortuousstructure that looks like a corkscrew consisting of internal cervical rings. The internal folds of the cervix form afunnel-like shape with a narrow opening projecting caudally into the cervical lumen which limits the passage ofinseminating pipette through cervical canal. The induction of cervical relaxation is investigated to allow deepercervical penetration. The most significant factor in cervical relaxation is the rearrangement of collagen fibresincervical extra cellular matrix and the changes in smooth muscle function. The application of exogenous substanceincreases the depth of cervical penetrability. Follicle Stimulating hormone (FSH), Hyaluronan, Misoprostol,Prostaglandin E2 (PGE2) or oxytocin is likely to induce the cervical relaxation during the periovulatory period inewes. The greater cervical penetrability ensures the success of TCAI.

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