Comparative patterns of follicle development and selection in ruminants.

Area of Science:

• Reproductive biology and endocrinology
• Comparative physiology
• Veterinary medicine

Background:

• Technological advancements in ultrasonography and molecular endocrinology have spurred research into ovarian function.
• Follicular dynamics in ruminant species beyond cattle remain understudied, with ongoing debate on follicular growth patterns and dominance.

Purpose of the Study:

• To establish the bovine model as a foundation for understanding ruminant follicular development.
• To compare follicular dynamics across various ruminant species (sheep, goats, muskoxen, cervids, camelids).
• To identify general principles of follicular dynamics applicable to all ruminants.

Main Methods:

• Comparative analysis of existing research on follicular dynamics in different ruminant species.
• Utilizing ultrasonography and molecular endocrinology data.
• Establishing the bovine model as a reference point.

Main Results:

• Follicular growth occurs in a wave-like pattern across ruminant species.
• Follicular wave emergence is linked to surges in follicle-stimulating hormone (FSH).
• Dominant follicle selection involves decreased FSH and increased luteinizing hormone (LH) responsiveness.

Conclusions:

• Despite species-specific differences, fundamental physiological phenomena in follicular dynamics are conserved among ruminants.
• Follicular waves continue until an LH surge, occurring at luteolysis or seasonal transition.
• Progesterone inhibits LH secretion and dominant follicle growth, while dominance is most pronounced in early and late follicular waves.