Follicle selection in sheep with breed differences in ovulation rate

Area of Science:

• Reproductive biology
• Animal genetics
• Endocrinology

Background:

• Ovulation rate is a key factor in sheep fecundity.
• High fecundity breeds exhibit genetic variations influencing ovulation.
• Understanding these variations aids in unraveling follicle development mechanisms.

Purpose of the Study:

• To explore mechanisms of antral follicle development in high fecundity sheep breeds.
• To investigate how genetic variations override natural ovulation rate restrictions.
• To identify factors regulating follicular development and gonadotrophic function.

Main Methods:

• Comparative analysis of genetic variations in sheep breeds with differing ovulation rates.
• Exploration of hormonal feedback mechanisms (inhibin, oestradiol, FSH) in Finnish Landrace.
• Investigation of the FecB gene's role in precocious follicle development.

Main Results:

• Two strategies identified: reduced hypothalamic-pituitary sensitivity to ovarian hormones and genes like FecB promoting numerous small antral follicles.
• Pharmacological manipulation (oestrogen/inhibin treatment/immunisation) can mimic feedback system changes.
• The FecB gene mutation is linked to increased ovulation rates via enhanced follicle development, though the specific mutation is unconfirmed.

Conclusions:

• Genetic variations in sheep provide valuable models for studying ovulation and follicle development.
• Understanding these mechanisms, particularly the FecB gene product, can advance research into ovarian follicle regulation.
• Targeting these pathways could offer strategies for improving reproductive efficiency in livestock.