The Reproductive System of a Mare

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The Reproductive System of a Mare

• Livestock Production, Equine Science, Advanced
  Animal Science

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Introduction to the Estrous Cycle

• The recurring reproductive cycle in many female
  mammals, including estrus, ovulation, and changes
  in the uterine lining.
• Differs from the menstrual cycle in that the
  endometrium is not shed
• Generally, species with estrous cycles are not
  sexually active when they are not in the estrus
  phase of their cycle

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The Estrous Cycle

• Estrus (Follicular) period when mare is
  sexually receptive to stallion, the heat stage
• Diestrus (Luteal) period when mare is not
  sexually receptive

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The Estrous Cycle (cont.)

• Helps the mare physically prepare for conception
• Generally, the cycles occur between spring and
  fall (when the days are longer)
• 18 - 21 days long

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Terminology

• Anestrus complete absence of estrus, prevents
  mares from conceiving during the winter months
• Seasonally polyestrus mares go through regular
  estrus cycles during part of the year

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The Parts

• Vulva the external opening of the reproductive
  canal
• Vagina 6-8 inch long muscular membrane
  connecting the vulva to cervix tissues are
  elastic to accommodate penis during breeding and
  foal during birth
• Cervix about 4 inches, elastic muscle, located
  behind vagina

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• Uterus contains 2 branches that are referred to
  as horns protects and nourishes the
  embryo/fetus
• Oviducts attached to each uterine horn
  transports the discharged egg from the ovaries
  the mares Fallopian tubes
• Ovaries 2-3 inch bean-shaped organs contains
  follicles that hold the mares egg cells

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Reproductive Anatomy
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During estrus.

• Vagina becomes relaxed and secretions increase
• Vulva relaxes
• Cervix increases secretions, opens, and relaxes
• Uterus becomes heavier, losing its tone, due to
  increased levels of estrogen

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Signs of Estrus

• Frequent urination
• Squatting posture
• Winking of labia
• Raising of tail
• Receptive toward stallion
• Discharge from vagina

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Breeding Tips

• Have a vet examine the mare and stallion for
  diseases and evaluate the chances of conceiving
• Wash the mares (and stallions) genitals with
  warm non-soapy water to minimize the chances of
  dirt and bacteria entering during the mating
  process
• Wrap the upper 1/3 of mares tail with a clean
  wrap so that there is a smaller chance of it
  getting in the way

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Breeding Methods

• Live Cover methods in which mare and stallion
  are physically brought together to breed
• Hand Mating most widely used people handle
  both mare and stallion
• Corral Mating mare and stallion are turned into
  a paddock where they mate naturally
• Pasture Mating stallion is turned out with a
  group of mares for the entire breeding season

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Alternative Breeding Methods

• Artificial Insemination (AI) mare is
  inseminated by a veterinarian
• Embryo Transfer removing the embryo from a mare
  and transferring it to a surrogate mare

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Artificial Insemination (AI)

• Pros

• Cons

• Semen sample from stallion can be used for more
  than one mare
• Frozen semen can be stored for long periods of
  time, making international breeding possible
• Chances of contamination in the mare is reduced
• Smaller chance of injury to both the stallion and
  mare

• Humans handle every step of this process, so
  there is a higher chance of human error
• Various competition organizations, such as The
  Jockey Club, does not allow competing horses to
  be bred through AI

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Important Hormones

• Estrogen
• Secreted by follicles
• Hormone that causes the pituitary gland to
  secrete more LH
• Makes mare more receptive toward stallion
• Prepares mare for conception physically
• Peaks 1-2 days before ovulation

• Progesterone
• Prevents conception and decreases the
  receptiveness of the mare to the stallion
• Causes cervix to close
• At its lowest level during the estrus phase
• Suppresses hormonal activity to maintain
  pregnancy (if mare is pregnant)
• If mare is not pregnant, the estrous cycle will
  continue

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More Hormones

• Luteinizing hormone (LH)
• Secreted by the pituitary
• Assists the maturation of the follicle
• Follicle stimulating hormone (FSH)
• Secreted by pituitary, transported through
  bloodstream to ovaries
• Stimulates the production of follicles

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