Reproductive System of the Horse (2)

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Presentation Transcript

Reproductive System of the Horse : 

Reproductive System of the Horse APSC 451 Equine Production

Reproductive System of the Horse : 

Reproductive System of the Horse Mare’s Reproductive System: Lies in a horizontal position within the abdominal and pelvic cavities and includes the: Vulva Vagina Cervix Ovaries Oviduct Uterus

Reproductive System of the Horse : 

Reproductive System of the Horse Vulva: External opening of the female reproductive tract Vagina: A 6-8 inch muscular tube lined with mucus membranes Connects the vulva to the cervix Tissues of the vagina are elastic to accommodate the stallion’s penis and birthing of the foal

Reproductive System of the Horse : 

Reproductive System of the Horse Cervix: Provides entrance to the uterus at the end of the vagina About 4 inches long When the mare is in estrus, the cervix is flaccid and open to facilitate the passage of semen When not in estrus, cervix is tightly closed and serve as a barrier to prevent foreign agents from entering the uterus

Reproductive System of the Horse : 

Reproductive System of the Horse Ovary: Primary reproductive organs Two, located at the upper end of the system They produce eggs Contains all the egg cells that the female will ever produce in her lifetime Each egg is contained in a follicle

Reproductive System of the Horse : 

Reproductive System of the Horse Oviducts or Fallopian tubes: Site of fertilization When the egg matures, the follicle ruptures and the egg is discharged The egg is trapped in a funnel-shaped membrane surrounding the ovary called the infundibulum The infundibulum narrows to form the oviduct Oviduct connected to the uterus and carries the egg there after fertilization

Reproductive System of the Horse : 

Reproductive System of the Horse Uterus: Largest of the female reproductive organs Capable of responding as the fetus grows Multi-layered, hollow and Y-shaped Base of the ‘Y’ is the uterine body Two branches are the horns

Uterus of the mare : 

Uterus of the mare

Reproductive System of the Horse : 

Reproductive System of the Horse Uterus cont’d: Three distinct layers: Serous layer- outer layer Myometrium- middle layer. Contains muscular tissue responsible for pushing the foal into the birth canal during parturition Endometrium- innermost layer. Contains rich supply of blood

Reproductive System of the Horse : 

Reproductive System of the Horse Hormones: Light jump starts the reproductive system by stimulating the hypothalamus to produce gonadotropin releasing hormone (GnRH) GnRH stimulates the pituitary to secrete follicle stimulating hormone (FSH) and luteinizing hormone (LH)

Reproductive System of the Horse : 

Reproductive System of the Horse Hormones, cont’d: FSH travels to the ovaries where it stimulates the production of one or more follicles When the follicles are ~ 20-25 mm in diameter, they secrete estrogen which stimulates sexual activity in the mare LH facilitates maturation and ovulation of the follicle

Reproductive System of the Horse : 

Reproductive System of the Horse Hormones, cont’d: After ovulation, estrogen levels drop The remains of the follicle (once the ovum has been released) forms a corpus luteum (CL) Granulosa cells in the CL produces progesterone Progesterone shuts down the estrus stimulating hormones

Reproductive System of the Horse : 

Reproductive System of the Horse Hormones, cont’d: Progesterone works to maintain the pregnancy The cervix is now closed and the mare loses interests in the stallion If the mare becomes pregnant, the uterus will remain under the influence of progesterone for about another 12-14 days

Reproductive System of the Horse : 

Reproductive System of the Horse Hormones, cont’d: If at that time pregnancy still did not occur, the uterine endometrium secretes the hormone prostaglandin Prostaglandins destroy the CL that is producing progesterone With progesterone production shut down, FSH levels will rise and the cycle starts again

Hormones : 

Hormones

Reproductive System of the Horse : 

Reproductive System of the Horse Breeding behavior: The mare is seasonally polyestrous – meaning she comes into heat several times/year, but does not cycle all year round They begin cycling in about January-February and continues until the breeding season peaks in about June-July

Reproductive System of the Horse : 

Reproductive System of the Horse Breeding behavior, cont’d: By September-October cycling is irregular and by November she stops and remain inactive during the winter The times of irregular and no cycling - called the transition months (anestrous) Estrus usually lasts 6-8 days during the spring and progressively shortens as it gets to the peak of the season

Reproductive System of the Horse : 

Reproductive System of the Horse Breeding behavior, cont’d: Estrous cycles usually starts at puberty which is usually about 15-24 months, although it can be as early as I year and as late as 4 years Normal estrous cycle for the mare is 21 -22 days

Reproductive System of the Horse : 

Reproductive System of the Horse Fertilization: Once ovulation occurs, the ovum is released and enters the oviduct where fertilization will take place Ovum remains viable for about 8-12 hours Spermatozoa entering the oviduct can live for 24-48 hours (sometimes longer) It takes 4-6 hours for the sperm to reach the ovum for fertilization to take place

Reproductive System of the Horse : 

Reproductive System of the Horse Fertilization, cont’d: After the egg is fertilized, it travels down the oviduct and enters the uterus in 5-6 days Embryo very mobile and moves from one uterine horn to the next by day 16-18, the embryo settles in one horn and implants

Reproductive System of the Horse : 

Reproductive System of the Horse Fertilization From ovulation to parturition, the average length of gestation is 335 days plus or minus 2-4 weeks Depends on season, nutritional status and sex of the fetus