Equine Reproduction

Definitions • Gestation: time of pregnancy. – Range 310-370 days • Parturition: Birthing process • Fertilization: when the egg meets the sperm and the zygote is formed. • Implantation: When the egg attaches to the wall of the uterine horn to get food

The Mare’s Reproductive System

Mares have complicated reproductive processes, and they do not easily become pregnant. Each mare has her own reproductive pattern, and knowing that pattern is the key to increasing the chances of fertilization.

Female Anatomy

• • Ovary: the main organ of reproduction. – kidney-shaped organs that produce hormones and the ova (eggs). – The ovaries are small and hard while inactive. Oviduct: a tube from the ovaries to the uterine horn. – When the egg reaches the oviduct it can be fertilized by sperm cells if they are present

• Fimbria:(infundibulum)funnel shaped end of the oviduct near the ovary; catches the egg and funnels it into the oviduct.

Female (dam) Anatomy

• Uterine Horns: area between the oviduct and the uterus. – Where implantation of the egg occurs • Uterus : area between the horns and the cervix – lined with the placenta that the growing fetus fills • Cervix: Tightly knotted muscle that regulates what enters or leaves the uterus – Dialates during parturition

Female Anatomy

• Vagina: area between the cervix and the vulva – Birth canal • Vulva: opening to the outside world • Clitoris: sensory organ

Female ReproductiveTract

Equine Reproduction Male (sire) Anatomy

1. Testes: –

Site of sperm production; produce the male hormone testosterone.

2. Scrotum: •

Protective sack around the testes; helps to regulate the temperature of the testes. The cremaster muscle contracts to draw the testes up toward the body during cold weather to keep them warm, and relaxes to lower them away from the body to keep them cool when the weather is hot.

Stallion 3. Epididymis: •

The site of sperm storage and maturation.

Stallion parts • 4. Vas deferens: –

The passageway for the sperm to pass from the epididymis to the urethra and accessory sex glands in the pelvic region.

• 5. Penis: –

The copulatory organ of the stallion.

Stallion Parts • 6. Prepuce: –

Loose surrounding skin that protects the free end of the penis.

• 7. Accessory sex glands: –

Contribute fluids that serve as a buffer and source of nutrients for the sperm cells: bulbourethral gland, prostate gland, vesicular gland.

Stallion

Stallion

• Libido stands for: Sex drive of a stallion • Spermatozoa mature in the epididymis

(GnRH) • gonadotropin releasing hormone • GnRH stimulates the secretion of the gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (LH)

• FSH and LH stimulate the ovaries

Gestation period Length - Horses • Range 310-370 days • Average 336 days

Progesterone • Hormone produced at the uterus to maintain the pregnancy.

Gestation period length • Knowledge of the length of gestation period is important to the producer because: a. it helps to regulate production cycles b. it helps in the planning of the breeding program c. it helps to predict the date of birth

Abortion • EXPULSION of the fetus before the time of PARTURITION.

Causes for abortions: • 1. Infections a. Bacteria and Fungi (ex., Rhinopneumonitis, Vibriosis) b. Viral (ex., influenza) c. Protozoans (ex., Trichomoniasis)

Causes for abortions: • 2. Genetic Abortions a. Occur when the fetus is malformed b. Dam's body usually rejects the malformed fetus for reasons unknown.

Causes for abortions: • 3. Injury related abortions a. Rare because fetus is well protected b. Prevent injuries caused by kicking, bumping, or squeezing

Causes for abortions: • 4. Nutrition Examples: - Poisonous Plants - Ration too low in required nutrients

Development • 3 periods of development from pregnancy to birth - Ovum Period - Embryonic Period - Fetal Period

Ovum Period ( Days 0 to 25 in horses) • 1. Fertilization • 2. Cell Division

Stages during the ovum period • Zygote – 2 to 8 cells

Stages during the ovum period • Zygote – 2 to 8 cells • Morula – spherical mass of cells (outer layer and central core)

Stages during the ovum period • Zygote – 2 to 8 cells • Morula – spherical mass of cells (outer layer and central core) • Blastula -- mass of cells with a hollow cavity

Embryo Period (Days 25 to 60 in horses) • 3. Implantation - the new embryo becomes implanted in the uterine horn where it will be nourished and develop.

Abnormal implantation • Ovarian: Young seldom survive to full term • Tubal: Young rarely survive to birth • Abdominal: Young do not survive to full term

Embryo Period • 4. Differentiation - cells become organized into specific structures

Embryo Period • 5. Completion of all major ORGAN systems.

Embryo Period • 6. Looks like the ORGANISM.

Fetal Period (Days 60 to 336 in horses) • 7. Placentation - MEMBRANES develop to provide the FETUS with NUTRITION.

• Each embryo usually has their own set of membranes

Placental Structures: •

Amnion

– inner most layer that forms a sac around the embryo/fetus. (Amniotic Sac) • Filled with amniotic fluid that protects young from shock and adhesion

Types of placental attachment •

Diffuse

– contact is made over most of the uterus • Mares, sows, humans

Placental Structures •

Umbilical Cord

- long FLEXIBLE tube attached to the placenta where FOOD, OXYGEN, and WASTES are exchanged between the MOTHER and the baby.

Placental Barrier • Placenta prevents large molecules from passing from mother to young.

• Viruses are small enough to penetrate as are certain other chemicals.

Fetal Period • 8. Growth and Development - the fetus GROWS and organs continue to DEVELOP so that the animal can LIVE on its OWN.

Parturition -the act of giving birth

Signs of birth in horses 1. 2-6 weeks prior, udder swells 2. 7-10 days prior, muscles shrink and abdomen drops 3. 4-6 days prior, teats fill with milk 4. 12-24 hours prior, “wax” appears on nipples (“waxing”)

Stages of Parturition (Labor) • Stage 1 - Preparatory Stage • Stage 2 - Expulsion of fetus • Stage 3 - Expulsion of the placenta • Stage 4 -Period of Rest

Preparatory Stage 1. Restlessness of animal due to minor contractions 2. Dilation of the cervix 3. Cervix expands allowing uterus and vagina to become a continuous canal

Expulsion of the fetus 1. Increased contraction (abdominal pressing marks) 2. Straining followed by a few minutes of rest 3. Fetus enclosed in amnion, propelled through birth canal and appears at vulva

Expulsion of the fetus 5. In horses, placental connections are broken. 2nd stage must be rapid

Expulsion of placenta (afterbirth) 1. Caused by uterine contractions 2. Placenta should be expelled within 12 hours following parturition

Expulsion of placenta (afterbirth) (foaling problems, abortion, twins, etc., may cause it to be retained) 3. Used to remove retained placenta by hand, now we treat it with antibiotics.

Stage 4

• Period of Rest

Proper Presentation • Most common is forelegs first with nose resting on the forelegs (anterior) • Mild labor pains usually start several hours before actual birth

Proper Presentation

Head and Hind legs Forward

Neck Presented

Proper Presentation • First water bag will appear on the outside increasing in size until it ruptures due to its own weight • Immediately after the first bag, the amniotic bladder (second water bag) follows, containing the fetus

Proper Presentation • Presentation of fetus after straining on the mares part • If presentation is normal and within 45 minutes to an hour hours after the first signs of foaling, then no assistance is necessary

• Always treat the umbilical cord with iodine after birth

Dystocia •

Difficulty

during parturition

Fetal Dystocia problems • Over sized fetus • Multiple births • Breech presentation • Deviations in normal presentation

Maternal dystocia problems • Narrowing of the birth canal due to fractures of the pelvis • Twisted uterus reducing size of birth canal • Cervix fails to dilate • Absence of uterine contractions – Caused by large litter size or exhaustion due to fetal dystocia

Stall preparation for birth • should be bedded with straw. • Wood shavings and other similar bedding materials should be avoided because they may stick to the foal's wet nostrils and suffocate it.

Should I lend assistance?

• What is the due date?

• How long has the animal been trying to give birth?

• Has the animal given birth before?

Should I lend assistance?

• Have some offspring already been delivered?

• Has anyone attempted to assist yet?

• Should I assist or call vet?

Postpartum Behavior Behavior

after giving birth

Postpartum Behavior in Mares • Following birth the mare often lies exhausted for 20-30 minutes • Mares do not eat the afterbirth, but will groom their foals

• Foals must nurse soon after birth to get the colostrum that has the antibodies for the immune system

Estrous Cycle

SEASONAL POLYESTRUS • During winter season, mares are in reproductive quiescence (or hibernation) called anestrus.

– will not respond to the stallion's attention During this season of reproductive activity, the mare will experience a series of estrous cycles.

Mares Estrous cycle •

cycles will repeat at 21- to 23-days

• Estrus (heat) lasts an average of five to seven days. –Estrus is characterized by receptivity to the stallion.