Reproductive System of the Horse

Page 1

• Title: Reproductive System of the Horse

• Course: APSC 451

• Department: Equine Production

Page 2

• Mare’s Reproductive System: Lies horizontally in abdominal and pelvic cavities, consists of the following components:

  • Vulva

  • Vagina

  • Cervix

  • Ovaries

  • Oviduct

  • Uterus

Page 3

• Diagram of Mare's Reproductive System:

  • Vagina

  • Cervix

  • Horn of Vulva

  • Vestibule

  • Bladder

  • Body of Uterus

  • Uterus

  • Ovary

  • Fallopian Tube

Page 4

• Vulva:

  • External opening of the female reproductive tract.

• Vagina:

  • A muscular tube (6-8 inches) lined with mucus membranes.

  • Connects the vulva to the cervix.

  • Elastic tissues accommodate stallion’s penis and foaling.

Page 5

• Cervix:

  • Provides entrance to the uterus, approximately 4 inches long.

  • Flaccid and open during estrus to facilitate semen passage.

  • Closed when the mare is not in estrus, serving as a barrier.

Page 6

• Ovary:

  • Primary reproductive organ, two located at the upper end.

  • Contains all egg cells a mare will produce in her lifetime; each egg is contained in a follicle.

Page 7

• Oviducts (Fallopian Tubes):

  • Site of fertilization.

  • Egg is discharged when the follicle ruptures, trapped by the infundibulum.

  • Oviduct carries fertilized egg to the uterus.

Page 8

• Uterus:

  • Largest female reproductive organ, responds as fetus grows.

  • Multi-layered, hollow, Y-shaped structure.

  • Two branches (horns) and a base (uterine body).

Page 9

• Parts of Uterus:

  • Uterine body

  • Uterine horn

  • Oviduct

  • Infundibulum

  • Ovary

  • Broad ligament

  • Cervix

  • Vagina

  • Vulva

Page 10

• Uterus Structure:

  • Three distinct layers:

    • Serous Layer: Outer layer.

    • Myometrium: Middle layer with muscular tissue for parturition.

    • Endometrium: Innermost layer with rich blood supply.

Page 11

• Estrous Cycle:

  • Normal cycle lasts 21-22 days:

    • Estrus Phase: Mare receptive to stallion, lasts 6-8 days.

    • Diestrus Phase: Mare not in heat, rejects stallion, lasts 14-15 days.

Page 12

• Cyclic Behavior:

  • Primary factor: increased hours of light.

  • Artificial lighting can regulate cycles.

  • Hormones control cycle.

Page 13

• Hormonal Control:

  • Increased light stimulates hypothalamus to produce GnRH.

  • GnRH leads to pituitary secretion of FSH and LH.

Page 14

• Follicle Development:

  • FSH stimulates ovaries to develop follicles.

  • Developing follicle secretes estrogen, stimulating sexual activity.

  • High estrogen triggers LH release from pituitary.

Page 15

• Ovulation:

  • LH causes follicle to rupture, releasing the ovum.

  • After ovulation, estrogen levels drop; corpus hemorrhagicum forms from the ruptured follicle.

  • Corpus luteum formed from luteinization of the hemorrhagicum.

Page 16

• Progesterone Function:

  • Produced by granulosa cells in the corpus luteum.

  • Shuts down LH release, maintains pregnancy.

  • Cervix closes; mare loses interest in stallion.

Page 17

• Cyclic Reset:

  • If mare does not conceive, progesterone influences uterus for 12-14 days.

  • Uterine endometrium secretes prostaglandin, causing corpus luteum regression.

  • FSH levels rise, restarting the cycle.

Page 18

• Pregnancy Recognition:

  • If conception occurs, embryo migration inhibits prostaglandin secretion.

  • Corpus luteum remains functional, maintaining progesterone levels for pregnancy.

Page 19

• Hormonal Pathway:

  • Diagram showing relationship between sunlight hours, pineal gland stimulation, hypothalamus, GnRH, pituitary hormones (FSH, LH), ovarian hormones, and roles in reproduction. Gondotropin Releasing Hormone

Page 20

• Breeding Behavior:

  • Mares are seasonally polyestrous, cycling several times/year.

  • Cycling begins in January-February; peaks in June-July.

Page 21

• Seasonal Cycling:

  • Cycling irregular by September-October; ceases in November (anestrous).

Page 22

• Estrous Cycle Initiation:

  • Begins at puberty (15-24 months), normal cycle is 21-22 days.

Page 23

• Fertilization:

  • Ovum viable for 8-12 hours post-ovulation.

  • Sperm can survive 24-48 hours in oviduct; takes 4-6 hours to reach ovum.

Page 24

• Embryo Development:

  • Fertilized egg travels to uterus in 5-6 days.

  • By days 16-18, the embryo implants in one horn.

Page 25

• Gestation Period:

  • Average gestation length: 335 days (+/- 2-4 weeks).

  • Influenced by season, nutrition, and the fetus' sex.

Page 26

• Stallion’s Reproductive System:

  • Main functions: produce sperm and testosterone, introduce sperm into mare.

Page 27

• Stallion's Anatomy:

  • Includes the prostate, vesicular glands, bladder, vas deferens, urethra, glans penis, scrotum, testicles, and epididymis.

Page 28

• Components of Male Reproductive System:

  • Two testes, accessory sex glands, tubules for sperm transport, and scrotum.

Page 29

• Detailed Male Anatomy:

  • Vesicular glands, prostate, ampulla, deferent duct, epididymis, bulbourethral glands, glans penis, and retractor penis muscle.

Page 30

• Testes Characteristics:

  • Two testes suspended by spermatic cord, ovoid shape (80-140 mm long, 56-80 mm wide).

  • Housed in scrotum, separated by a septum.

Page 31

• Testicular Descent:

  • Testes should descend into scrotum by 3 weeks gestation or 2 weeks post-birth.

  • If not, it results in cryptorchidism.

Page 32

• Penis Structure:

  • Organ of copulation, consisting of three parts: root, body (shaft), and glans penis (enlarged end).

Page 33

• Sperm Production:

  • Occurs in seminiferous tubules of testes, billions produced daily.

Page 34

• Epididymis Function:

  • Transports, matures, and stores sperm from testes.

  • Deferent ducts transport sperm to accessory glands, adding fluids to semen.

Page 35

• Leydig Cells:

  • Produce testosterone, present in interstitial tissues of seminiferous tubules.

  • FSH and LH also involved in stallion's reproductive processes.

Page 36

• Mating Process:

  • Involves three basic processes: erection, emission, and ejaculation.

Page 37

• Sperm Maturity:

  • Full production begins at over a year old, reaches capacity at about 4 years; remains constant until age 20.

Page 38

• Factors Influencing Sperm Production:

  • Season, testicular size, age, frequency of ejaculation.

Page 39

• Seasonality in Stallions:

  • Stallions are seasonal breeders, sperm production year-round.

  • Best months for testicular size: May, June, July.

Page 40

• Sperm Count Variation:

  • Sperm count drops significantly in December-January compared to June-July.

  • Stallions should be exposed to 16 hours of light daily to optimize breeding conditions.