Influence of breed and age on morphometry and depth of inseminating catheter penetration in the ewe cervix: a postmortem study.

A detailed examination of the cervical canal in the ewe was carried out. This analysis could be used to design new catheters for artificial insemination (AI) to achieve deeper cervical penetration and therefore better fertility results. Three hundred and sixty-five cervices from four sheep breeds (Churra, Assaf, Merino, Castellana) obtained postmortem were used. Cervix morphometry and depth of cervical penetration using two types of catheters were determined. A conventional straight catheter for ovine artificial insemination (IMV), and a bent catheter, ending in a stainless steel needle, 9 cm in length and with an 8 mm tip bent 45 degrees , were used. The results showed that the morphometry of the cervix depends on breed and age of the ewe. The cervices of Churra breed were shorter and narrower, and had a higher number of folds than those of other breeds. Postmortem cervical penetration was deeper when the cervices were longer and wider, and with fewer folds (Merino and Castellana breeds). In ageing ewes, the cervix tended to become longer and wider, with loose folds. This decreased structural complexity and significantly improved cervical penetration. The bent catheter allowed significantly greater cervical penetration than the straight IMV one.