Abstract

In sheep, cervical artificial insemination (AI) involves depositing semen at the cervical opening, as it is not possible to traverse the cervix due to its complex anatomy. However, internationally this method yields low pregnancy rates when frozen-thawed semen is used. An exception to this is in Norway, in which vaginal deposition of frozen-thawed semen to a natural estrus yields pregnancy rates around 70%. As the cervix and its secretions are the principal factors influencing sperm transport to the site of fertilization the aim of this study was to characterise the differences in the cervical anatomy as well as the cervicovaginal mucus properties of six European ewe breeds across three countries known to have differences in pregnancy rates following cervical AI with frozen-thawed semen. These were Suffolk and Belclare in Ireland, Fur and Norwegian White Sheep (NWS) in Norway and Ile de France and Romanov in France (n = 28–30 ewes/breed). Cervicovaginal mucus was collected at the follicular and luteal phases of both a synchronized and natural cycle and assessed for mucus weight, viscosity and colour. The anatomical characteristics of the cervix (length of the cervix, number of cervical rings and the appearance of the external os) were assessed post-mortem. There was a type of the cycle by ewe breed interaction represented by no differences in mucus production between ewe breeds at the natural cycle for both the follicular and luteal phases of the cycle. However, there were differences between ewe breeds at the synchronized cycle (P < 0.05). Belclare had the lowest mucus production at the follicular phase while NWS had the lowest amount of mucus at the luteal phase of the synchronized cycle. Overall, across all ewe breeds, mucus production was higher at the follicular than at the luteal phase (P < 0.05). Despite reports of Suffolk and NWS having the most divergent pregnancy rates following cervical AI with frozen-thawed semen, both breeds had the lowest overall mucus viscosity at the follicular phase of both types of cycle with no differences between both ewe breeds (P > 0.05). The length of the cervix, number of cervical rings and the external os type were affected by ewe breed (P < 0.05). Suffolk ewes had longer cervices but lower number of cervical rings than NWS and Fur ewes (both with higher pregnancy rates). In conclusion, while mucus production and mucus viscosity was affected by breed, these changes are not consistent with the known differences between ewe breeds in their pregnancy rates following cervical AI with frozen-thawed semen.

Highlights

  • The main aim of this study was to ascertain if the reason why cervical/vaginal artificial insemination (AI) works well in some ewe breeds but not in others is related to the cervicovaginal mucus properties and/or gross cervical anatomical parameters

  • The results of the present study showed differences in mucus production between ewe breeds at the synchronized cycle while there were no differences at the natural cycle

  • There were no differences in mucus viscosity between Suffolk and Norwegian White Sheep (NWS), despite the differences in pregnancy rates following cervical AI with frozen-thawed semen

Read more

Summary

Introduction

This is evident in cattle where there is an easy to use transcervical insemination method using frozen-thawed semen, which farmers/technicians can perform themselves on-farm and yields similar pregnancy rates/AI to natural mating. In cattle penetrating the cervix with an AI pipette and depositing the semen in the uterine common body or into the uterine horns is essential to achieve high pregnancy rates [1]. The only effective method for AI in sheep using frozen-thawed semen is laparoscopic insemination, in which the semen is deposited into the uterine horns This is an invasive surgical procedure and requires veterinary expertise, which limits its use to genetic improvement programmes involving high value animals

Objectives
Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call