Evaluation of gross anatomical features of cervix of tropical sheep using cervical silicone moulds

The lambing rate obtained following cervical artificial insemination (AI) with frozen semen in sheep is low mainly due to the inability of frozen-thawed sperm to traverse the tortuous nature of the cervical canal. Although acceptable fertility has been attained by circumventing the cervical barrier through laparoscope aided intrauterine AI, the emphasis is currently given on the development of alternate non-invasive transcervical AI procedures. The complex anatomy of the cervix does not facilitate easy transcervical passage for an insemination catheter. The aim of the present study was: (i) to examine the gross anatomy of the cervix in slaughtered ewe lambs and adult ewes of the native Malpura and Kheri breeds raised under semi-arid tropical environment; and (ii) to cast silicone moulds of the reproductive tracts for measuring the dimensions of the cervix. Eighty reproductive tracts were excised immediately from carcass of Malpura and Kheri ewes and the external os of each one was classified depending on their appearance as duckbill, spiral, rosette or flap. The cervical canal of each tract was filled with a silicone sealant for casting the mould. Fifty complete silicone moulds were obtained representing 25 from ewe lambs and 25 from adult ewes. The mean lengths of the cervical mould of ewe lambs and adult ewes were 3.8+/-0.12 and 5.3+/-0.15 cm, respectively. The average number of funnel shaped folds in the cervical mould of ewe lambs and adult ewes were 3.2+/-0.19 and 3.4+/-0.22. However, the second and third-folds from the os were observed to be accentric in both ewe lambs and adult ewes. The information generated in this study would be useful for increasing the success rate of penetration in ewes exhibiting estrus in order to improve the lambing rate of tropical ewes following transcervical AI.