1. The Reproductive System of a Mare
Livestock Production, Equine Science, Advanced Animal Science
Have students fill in their diagram to the best of their ability.

2. 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

3. 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

4. The Estrous Cycle (cont.)
Helps the mare physically prepare for conception
Generally, the cycles occur between spring and fall (when the days are longer)
days long

5. 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

6. 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
See if Slides 6 and 7 help the students label the parts of the reproductive system

7. 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 mare’s Fallopian tubes
Ovaries – 2-3 inch bean- shaped organs; contains follicles that hold the mare’s egg cells

8. Reproductive Anatomy
Pause on this slide to give students time to complete their diagrams correctly.

9. 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
Use the diagram to point out each organ as you are discussing its function.

10. Signs of Estrus Frequent urination “Squatting” posture
Winking of labia
Raising of tail
Receptive toward stallion
Discharge from vagina

11. Breeding Tips
Have a vet examine the mare and stallion for diseases and evaluate the chances of conceiving
Wash the mare’s (and stallion’s) 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 mare’s tail with a clean wrap so that there is a smaller chance of it getting in the way
SOAP is never used because it can kill sperm cells. This drastically decreases the chances of pregnancy.

12. 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
Video of horses mating:

13. 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
The AI procedure:

14. 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

15. Important Hormones Estrogen – Progesterone – 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

16. 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
For more information on hormones: