ANSI 3543 - Equine Breeding and Foaling Final

Why should we understand the reproductive cycle?

- Economic investment in breeding mares

- Breeding your own mare or sending mare to breeding facility

Describe the reproductive cycle in a mare.

- They are seasonally polyestrous (have more than one estrous cycle during a specific time of year)

- Long day breeders

Describe what long day breeders are.

- Cycle when daylight is long

- "Shut down" in winter

- Begin cycling in spring

- As length of daylight increases mares transition and ovaries become active and grow larger follicles

- Mares have 3-4 intervals of estrus during transition but do not ovulate during this time

- End of transition = surge of LH and ovulation occurs - established estrous cycle after this

What is the term for the entire reproductive cycle in a mare?

Estrous

What are the three stages of the mares reproductive cycle?

- Anestrus

- Diestrus

- Estrus

What stage in the reproductive cycle is this?

Complete inactivity in cycle, usually during winter

Anestrus

What stage in the reproductive cycle is this?

Period of inactivity between periods of estrus

Diestrus

What stage in the reproductive cycle is this?

Period of sexual receptivity with follicular activity and ovulation

Estrus ("in heat")

What is the length of the estrous cycle?

- Ovulate every 21 days of cycle and occurs 1-2 days before end of estrus

- Estrus length is usually around 3-7 days

- Diestrus lasts around 15-17 days

What hormone is responsible for behavior signs of receptivity to a stallion, highest during estrus, and is produced by follicles on the ovary?

Estrogen

What hormone is responsible for upregulating levels of LH and FSH, and is produced by the hypothalamus?

Gonadotropin release hormone (GnRH)

What is the primary hormone responsible for ovulation and is produced by the anterior pituitary?

Luteinizing hormone (LH)

What hormone is responsible for follicular development in the ovary and is produced by the anterior pituitary?

Follicle stimulating hormone (FSH)

What hormone is responsible for recognition and maintenance of pregnancy up to about 150 days (placenta provides pregestins for maintaining pregnancy after 150 - term), and is produced by the corpus luteum (CL)?

Progesterone

What hormone is responsible for inhibiting progesterone. It "kills" the CL and is produced by the uterus (endometrium to be specific)?

PGF2a

How do we check for pregnancy?

- Use an ultrasound

- Before ultrasounds pregnancy was checked by manual rectal palpation

Describe how an ultrasound works and what the colors we see represent.

- Uses high frequency sound waves to create an image from the inside of the body

- Sound waves are safe for checking pregnancy

- Results seen on screen reflect density of tissue

- Fluid will appear black

- Tissue will appear shades of gray

- Bone would be white

What steps do we take to get a mare bred?

- Mare properly cycling

- Follicle size & consistency, edema, uterine tone, cervical tone all coincide with current cycle and are consistent for what is normal for that mare

- Breed just prior/during ovulation (24 hours before ovulation would be ideal)

- Check for ovulation

- Pregnancy checks

What do we need to see in a mare to make the right breeding decisions?

Need to look at the complete picture

- Follicle size (relative to mare, min 35 mm +)

- Edema (grades 1-3, increases prior to ovulation)

- Uterine tone

- Cervical tone (A v. B v. C)

- Fluid present

- Where at in cycle

- Collection schedule

- Fresh, cooled or frozen semen

How early can you accurately detect pregnancy and how would you do it? What are you looking for when you check for pregnancy?

- 14-18 days after a mare's last breeding or in other terms after ovulation

- Manual palpation would be 18-21 days post-breeding

- Can't feel anything that would indicate a pregnancy aside from uterine and cervical tone that would match pregnancy

- Ultrasounds are the most effective to look at each piece plus see the embryonic vesicle

- Can check for presence of CL and other factors

What happens to the embryo in early pregnancy checks?

During early days of embryonic development the embryo will migrate back and forth between the uterine horns and body

Why is it important that the embryo migrates back and forth between the uterine horns and body?

- Important for maternal recognition of pregnancy

- Embryo secretes substance that prevents uterus from releasing PGF2α

- Important because PGF2α would release naturally around day 17 of estrous cycle

- Migration slows around day 15

When does the embryo fixate in the uterus?

- Embryo fixates at 16-17 days

- Uterine tone will increase + thickening of uterine wall

- Understanding this timeline and characteristics is good to note in your records

- Checks for twins

- Embryo or cysts

When do we check for the heartbeat in pregnancy?

- Heartbeat can be seen as early as day 24

- Second pregnancy check evaluates a heartbeat and viability of a healthy fetus

- Can do other checks past heartbeat to make sure mare is still in foal

What are the different breeding techniques used in the equine industry?

- Live Cover (Pasture or hand mating)

- Artificial Insemination (Fresh semen, Cooled semen, or Frozen semen)

- Deep Horn Insemination (AI)

- ICSI (Intracytoplasmic Sperm Injection)

- Embryo Transfer

What is the procedure for artificial insemination?

- Load your mare in the stocks

- Wrap tail & hold/tie

- Clean & sterilize vulva

- Glove up & get rod ready

- Sterile & non spermicidal lube on hand

- Swipe back of hand of lube onto vulva

- Gently insert hand through vulva

- Scan for cervix

- Pass fingers gently through cervix

- Guide rod past fingers further past cervix

- Plunge semen through rod

- Gently pull back rod under fingers and pull out

What are some pros of artificial insemination vs. other breeding techniques?

- Can breed to variety of genetics in the industry

- Can breed several mares to same stallion

- Closely managing mare for success

- Controlling and creating sterile environment

- Not jeopardizing success rate compared to natural mating if handled correctly (50-60% pregnancy per cycle fresh, 45-55% pregnancy per cycle cooled, Can be up to 65-75%)

What are some cons of artificial insemination vs. other breeding techniques?

- Requires close management = more money spent in managing

- Working around collection schedules and timing of ovulation

- Need assistance of veterinarian

- Requires a lot of communication with multiple parties

What is deep horn insemination?

- Use flexible Al rod

- Initially pass rod traditionally through cervix

- Palpate rectally to locate tip of rod and help guide rode into the uterine horn on ovulatory side

- Rod advanced until at end of uterine horn near the entrance of the oviduct

When would you use deep horn insemination in mares?

- Used in cases of having low dose or bad quality semen & frozen semen

What does ICSI stand for?

Intracytoplasmic Sperm Injection

When would you use ICSI?

Used in cases of a stallion that has low sperm numbers or poor sperm quality

Describe the process of ICSI

- Micro injection of a single sperm cell into the cytoplasm of a mature oocyte

- Fertilized oocyte is incubated until it develops into an embryo (6-8 days)

- Embryos produced through ICSI can be transferred into a recipient mare, the original donor mare, or frozen for transfer at a later time

Why is ICSI not as popular as other techniques?

- Roughly $3,500 if using original mare as recipient

- Price of location where all procedures are done on site

- Also depends how long mare is managed on site

- If using recipient mare not owned fees of leasing will be added

When do you typically see people use embryo transfer?

- Used for mares with reproductive issues, older mares, or performance mares

- Increase in registration acceptance of embryo transfer foals + can register more than one foal out of one mare in a year now

Describe the process of embryo transfer.

- Breed mare then flush the embryo 7-8 days after ovulation

- Flush with lavage

- Filter at end of outflow tube

- Fluid in filter is searched for embryo under microscope

- After proper handling and washing of embryo it will be immediately transferred into recipient

- Complicated process since recipient has to be in same stage of cycle as the donor mare

- Cost roughly $ 5,000- $ 7,000

What is this anatomical part of the penis?

- Out pouching of skin that contains the testes

- Covers and protects testes

- Regulates temperature of testes

- Temperature regulation is very important for spermatogenesis (production of sperm)

- Multiple layers

Scrotum

What are the three layers of the scrotum and their functions?

Tunica Dartos

- Muscle that helps drop or raise scrotum for temperature regulation

Parietal & Visceral Vaginal Tunica

- Layers of tissue that surround each testicle

Testicular Parenchyma

- Tissue in the center of the testes that contains the seminiferous tubules

What is this anatomical part of the penis?

- Responsible for production of sperm and androgenic hormones like testosterone

Testes

How long does the process of sperm production take?

2 months

What are the two parts of the parenchyma (center of testes)

- Seminiferous tubules

- Interstitial tissue

Describe the seminiferous tubules.

- Site of sperm production

- Sertoli cells within seminiferous tubules help develop and mature germ cells into sperm

What is the interstitial tissue in the testes?

- Contains leydig cells, fibroblasts, lymphocytes, blood vessels and lymphatics

- Leydig cells produce testosterone

- Testosterone is important for sperm production and male behavior

What is this anatomical part of the penis?

A duct that runs across the testicle Divided into the head, body, and tail

Epididymis

Where in the epididymis is sperm stored?

Sperm is stored in the tail

What happens as sperm passes through the epididymis?

- Sperm mature as they pass through the epididymis

- When sperm first enter epididymis they are not motile and not capable of fertilization

- They become motile and able to fertilize as they pass through

- Sperm are in a " sleep " state while stored in the tail

- Sperm move to vas deferens during ejaculation

- After contact with seminal plasma during ejaculation sperm become motile

What is this anatomical part of the penis?

It has 3 parts: Vas deferens, Cremaster muscle, Pampiniform plexus

Spermatic chord

What is the vas deferens?

Muscular tube that moves sperm from epididymis to the ampulla

What is the cremaster muscle?

Raises and lowers testes

What is the pampiniform plexus?

- Composed of single artery surrounded by veins

- Helps with thermoregulation

What are the four accessory glands in the stallion?

Ampulla

Vesicular glands (seminal vesicles)

Prostate gland

Cowpers gland

How much of the fluid in the ejaculate comes from secretions from the accessory glands? What is it called?

- Secretions from accessory glands make up majority of the fluid in the ejaculate

- Called the seminal plasma

What fluid is secreted after ejaculation and where does it come from?

- The gel fraction follows the ejaculate

- Comes from the seminal vesicles

- Vas deferens

- Ampulla

- Semen

The penis is composed of how many parts?

7 parts

What is the tunica albuginea?

Connective tissue

What is the corpus cavernosum?

Fills with blood during erection and enlarges

What is the corpus spongiosum?

Spongy erectile tissue surrounding penile urethra

What is the urethra?

Duct that semen and urine pass through

What is the bulbospongiosum muscle?

Helps move ejaculation and urine out of the penile urethra

What is the retractor penis muscle?

Responsible for retracting and relaxing the penis from the sheath

What is the glans penis

Enlarged free end of the penis Can help seal cervix during ejaculation and deposit ejaculate in the uterus

Why do we perform a breeding soundness exam for a stallion?

- Estimate future reproductive potential

- Knowledge about stallion before purchase

- Check for venereal diseases

- Determine causes of poor reproductive performance

What is included in a breeding soundness exam for a stallion?

- General health

- Reproductive history

- Behavior

- Mating ability

- Genital examination

- Semen evaluation

What is evaluated in a breeding soundness exam for a stallion?

- Examine the external genitalia (penis, scrotum, testes)

- Measure testicular size to estimate potential sperm production

- Helps determine the daily sperm output to know how many mares he can breed in a day, year, etc

- Testicular size is highly heritable

- Evaluate libido & mating ability (erection within 2 minutes)

- Make sure stallion can successfully be collected

- Evaluate semen (color, concentration, volume, pH, sperm motility, morphology)

- Rested stallions may have low motility and poor morphology

- Optimal semen quality usually reached in 5-7 days of consistent collection

What are the final classification of breeding stallions after a breeding soundness exam?

- Satisfactory (75-80 % or greater preg rate)

- Questionable (could have difficulty but problems detected might resolve over time with or without treatment)

- Unsatisfactory (issues that would highly decrease fertility or pass undesirable heritable traits)

What is a bacterial exam for venereal disease?

- Contagious equine metritis (CEM) from Taylorella equigenitalis

- Spread through AI, natural sevice, contaminated equipment

- Stallion show no signs of infection, but mares with have vaginal discharge and can be unable to conceive

- Non-lethal, asts a few weeks, treated with antibacterial wash

What is a viral exam for venereal disease?

- Equine viral arteritis (EVA) Equine Herpesvirus-3

- Mostly spread through respiratory secretions

- Can be transferred through virus infected semen

- Non lethal for mature horses, but causes abortion in mares or foal death

- Can cause sores on the studs penis

- Make sure the stallion has been vaccinated before breeding

- Most common in Standardbreds and warmbloods

What are some variables for collection success that you might observe?

- Good handlers

- Successful washing and tease

- Consistent environment and program

- Hot mare (stallions do sometimes have preferences)

- Proper AV preparation (Temp, lube, pressure)

- Proper handling of semen post collection

What is the breeding dose for fresh semen or cooled shipped semen?

500 million live progressively motile sperm cells

What is the breeding dose for frozen semen?

1 billion live progressively motile sperm cells

What is extender and why is it used in semen?

- Extender always added to shipped cooled or frozen

- Helps sperm handle cold shock, provides energy source, prolongs motility and viability

What are the components of extender?

- Lipoprotein (usually egg based or yolk based)

- Antibiotics

- Sugar source

- pH buffer

- Extender volume can be calculated or added at a 1:1 ratio

What type of semen is utilized in situations that include live cover but can also be used for artificial insemination?

Fresh semen

What are some benefits of using fresh semen?

- Higher chance of maintaining motility and viability

- Less processing needed

What are some disadvantages of using fresh semen?

Mare has to be on site

What type of semen is most commonly used in many segments of the horse industry?

Cool shipped semen

What percent of stallions have semen that handles the cooling process good?

70-80 % of stallions have semen that cools adequately

Motility decreases how much after 24 hrs of cooled storage for most stallions?

20-30%

What are some benefits of cool shipped semen?

- Mare does not have to be on site of stallion location

- Reduced cost by providing mare care at home

- Wide access to stallions

- If processed correctly, most sperm can last at least 24 hr without reducing ability to fertilize

What are some disadvantages of cool shipped semen?

- More intensive veterinary management to time shipment with mare's cycle

- Hormone therapy usually required

- Not all stallion semen handles cooling well

- Ratio of semen to extender added can greatly impact fertility

What are some benefits of using frozen semen?

- Mare does not have to be on site of stallion location

- Reduced cost by providing mare care at home

- Wide access to stallions

- Long - term storage

- Readily available

- Can be shipped in advance

- Can continue genetics of stallions that have passed

What are some disadvantages of using frozen semen.

- Not all stallions freeze well

- No tests for predicting fertility of frozen semen

- Pregnancy rates are generally lower compared to fresh or cooled semen

- Processing takes very specialized steps and skills

- Proper thawing process critical before insemination Inseminate within 6 hours of ovulation