Veterinary Theriogenology Quiz

Theriogenology

• Branch of Veterinary Medicine focusing on animal reproduction (physiology & pathology) and clinical practice (obstetrics, gynecology, andrology).

Veterinary Obstetrics

• Deals with medical and surgical care of female animals throughout breeding, gestation, labor, puerperium, and neonatal care.

Veterinary Gynecology

• Focuses on diseases of female reproductive organs (vagina, uterus, ovaries) and their treatment/prevention.

Andrology

• Medical specialty addressing male reproductive health issues.

Reproductive Physiology of the Female

• Most animals breed once a year, with parturition timing linked to optimal conditions for offspring.
• Neonatal period coincides with increased light/warmth and abundant maternal food.
• Reproduction requires: mating, attraction of the male, and sexual receptivity (estrus).

Estrous Cycle

• Animals have recurring periods of sexual receptivity (estrus cycles).
• Ovulation (release of oocyte) occurs in follicles ripening in the ovaries.

Phases

• Proestrus:

  • Increased reproductive activity;
  • Follicle maturation/corpus luteum regression (polycyclic species);
  • Uterus enlarges slightly, endometrium congested/edematous, increased gland activity;
  • Vaginal mucosa hyperemic; epithelium layer increase/cornification;
  • External visible signs in bitches (vulvar edema, hyperemia, discharge).

• Estrus:

  • Period of mating acceptance;
  • Onset/end accurately pinpoint cycle length;
  • Female seeks out male;
  • Increased mucus secretion from uterine/cervical/vaginal glands;
  • Vaginal/endometrial hyperemia/congestion; relaxed cervix;
  • Ovulation occurs in all species except cows (approximately 12 hrs post-estrus end).

• Metestrus:

  • Phase following estrus;
  • Luteinization (follicle cells transform into lutein cells, forming corpus luteum);
  • Reduced mucus secretion from genital glands.

• Diestrus:

  • Corpus luteum functional phase;
  • Increased uterine gland activity (hyperplasia and hypertrophy);
  • Tightened cervix;
  • Reduced/sticky secretions;
  • Pale vaginal mucosa;
  • Elevated progesterone levels from functional CL.
  • Luteal (CL) phase; differentiating it from follicular phase.

• Polyestrous Species:

  • Cycle divided into estrus, interoestrus, proestrus, metestrus, and diestrus.

• Anestrus:

  • Prolonged period of sexual rest;
  • Genital system quiescent; minimal follicular development;
  • Regressed/nonfunctional CL;
  • Scant/tenacious secretions; contracted cervix; pale vaginal mucosa.

Natural Regulation of Cyclical Activity

• Hypothalamic-Pituitary-Ovarian Axis (HPO): central control of cyclical activity.

• Extrahypothalamic influences: cerebral cortex, thalamus, midbrain (light, olfaction, touch).

• Uterine influence on the ovary.

• Factors impacting cyclical activity:

  • Seasonality
  • Hypothalamic/Anterior Pituitary Hormones
  • Folliculogenesis
  • Ovarian steroids
  • Ovulation, Corpus luteum formation
  • Luteolysis (corpus luteum regression)
  • Leptin
  • Insulin-like growth factors system
  • Prolactin
  • Role of opioids
  • Ovarian reserve and aging.

• Seasonal Regulation:

  • Pineal gland (melatonin) regulates reproductive activity in seasonal breeders (short vs. long days).
  • Melatonin levels (increased darkness) drive response in short day breeders (goats, sheep).
  • Decreasing melatonin drives stimulation in long day breeders (horses).

• Hypothalamic Regulation

  • Kisspeptin (neuropeptide): gatekeeper for GnRH release; affecting puberty timing and gonadotrophin secretion in seasonal breeders.