Mare Reproductive Physiology & Veterinary Procedures Study Notes

Mare Reproductive Physiology & Veterinary Procedures

Introduction

  • Presented by: Audrey A. Kelleman, DVM, Diplomate, American College of Theriogenologists, UF Veterinary Hospitals.

Estrus

  • Definition: The period of sexual receptivity in female mares.
  • Behavioral aspects of estrus.
  • Discussion on diestrus and its significance in the reproductive cycle.

Anatomy and Physiology

Vulva Anatomy
  • Importance of understanding vulvar anatomy in reproductive examinations.
Vestibule Anatomy
  • Related structures involved in reproductive physiology.
Transrectal Examination
  • Significance of transrectal palpation in veterinary practice.
  • Techniques for performing transrectal examinations in mares.
Transrectal Ultrasound
  • The necessity of adequate ambient light for optimal imaging.
  • Observations on room lighting affecting ultrasound clarity; suggestions for a taller cart for better visualization of the screen.
Ultrasound Anatomy Labels
  • Extensive anatomical labels involved in mare reproductive physiology:
    • Bladder (b)
    • Broad ligament (bl)
    • Cervix (ex)
    • Glans clitoris (gl)
    • Labia (l)
    • Constrictor vestibuli (cv)
    • Infundibulum (inf)
    • Left ovary (lo)
    • Left uterine horn (luh)
    • Ovarian artery (oa)
    • Oviduct (od)
    • Ovulation fossa (of)
    • Proper ligament of ovary (plo)
    • Tubal membrane (tm)
    • Uterine artery (ua)
    • Uterine body (ub)
    • Urethral orifice (uo)
    • Ureter (ur)
    • Vagina (va)
    • Vestibule (ve)
    • Vaginal fornix (vf)
    • Vestibular gland openings (vgo)

Reproductive Biology of the Mare

  • Key reference: "Reproductive Biology of the Mare, 2nd ed., 1992, OJ Ginther."
  • Understanding the equine ovulation fossa and its clinical relevance.
Ovulation Fossa
  • Description: The ovulation fossa is a critical area for palpation during reproductive examinations.
  • Importance in diagnosing breeding soundness.
Hypothalamic-Pituitary-Gonadal (HPG) Axis
Hormonal Regulation
  • Hypothalamus: Secretes Gonadotropin-Releasing Hormone (GnRH).
  • Anterior Pituitary: Releases Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).
  • Ovary: Produces inhibin, estrogen, and progesterone.
  • Hormonal interactions crucial for ovulation and reproductive cycles.
Seasonality & Photoperiod Effects
  • Connection between seasonality and the reproductive cycle in mares.
  • Pineal Gland & Melatonin:
    • Role of melatonin in regulating reproductive functions.
    • Melatonin is categorized as an indoleamine hormone.
Seasonal Influence Diagram
  • Indication of anovulatory season and its phases:
    • Fall transition
    • Winter anestrus
    • Spring transition

Estrous Cycle

Phases of Estrous Cycle
  • Key phases and their hormonal characteristics:
    • Follicular Phase: Hormonal activity leading to estrus.
    • Estrus: Highest levels of estrogen.
    • Ovulation: Triggered by a preovulatory LH surge.
    • Luteal Phase: Formation of Corpus Luteum (CL) and progesterone secretion.

Hormonal Concentrations in Mare Physiology

Estrogen Levels
  • Graphical depiction of circulating estrogen levels (ng/ml) during various days of the cycle.
  • Correlation of estrogen to estrus behavior and ovulation phases:
    • Peak at ovulation.
Progesterone Levels
  • Analysis of progesterone levels (ng/ml) across the estrous cycle.
  • Role of progesterone in maintaining pregnancy.

Pathways to Pregnancy and Parturition

General Conceptual Framework
  • Interactions between various hormones:
    • GnRH stimulates LH and FSH.
    • Inhibin's role in feedback mechanism affecting FSH release.
Follicular Development Process
  • Detailed representation of proestrual follicular development and estradiol’s role in reaching threshold levels.
  • Preovulatory LH surge leading to ovulation.

Corpus Luteum Development

  • Transition to diestrus and its role in the reproductive cycle.
  • Variability in appearance and functionality of the Corpus Luteum across different mares.
Diestrus Uterus Examination
  • Clinical observations during the diestrus phase and its physiological implications.

Conclusion

  • Importance of understanding reproductive physiology for veterinary practices in equine reproduction.
  • Emphasis on the integration of anatomical, physiological, and clinical knowledge in veterinary education and practical applications.