Floor: should provide good footing to prevent slipping, and concussion force on the dismount

Phantom: should be located near a mare enclosure so a mare can be in sight of the stallion if needed.

Laboratory: should be close to the collection area and equipped with a microscope, semen counter, hot and cold water, sinks, incubator, and storage area

2) Artificial Vagina:

• Also called AV, it is a water filled device used to simulate the mare’s reproductive tract, and facilitate the collection of semen from the stallion.

• It is a tubular, double lined rubber bladder that holds warm water and a semen-collecting bottle.

• When the stallion mounts the mare or phantom, the AV is placed on the stallion's penis and he works the AV as if he were breeding a mare.

• When ejaculation occurs; the semen passes through a filter into a collection bottle. The semen is then taken into the lab for processing. The most commonly used AV is the Colorado type. Developed by CSU

3) Mount Sources:

• Live mare: the most desirable ones are experienced, quiet mares that are in heat, or spayed mares on estrogen therapy can be used

• Phantom: most stallions can be trained to readily accept a phantom in place of a live mare to mount for collection. Some require a mare in heat in close proximity. Advantages of a phantom include:

1) Live mare in heat is not required for collection

2) Reduced risk of injury to stallion/mare and personnel.

3) A stallion with back or hind leg pain can have the phantom adjusted height wise to help in collection.

COOLED SEMEN

The introduction of cooled semen in the horse breeding industry has dramatically changed the process of selecting a suitable stallion to sire your next foal. Finding the right sire can be difficult when you are trying to match the current trends in the industry with your budget and the geographical location of the most desirable stallions. Often the stallion you want to breed to is in Texas, California, New York or as far away as Europe or Australia

Not long ago it would have required a long expensive haul to get your mare bred to such a stallion, however times have changed. The advent of shipped semen and frozen semen has dramatically and permanently changed the face of the horse breeding industry. Geography will no longer dictate which mares a stallion will breed. All major breeds except Thorobreds have approved the use of cooled semen for breeding mares.

ADVANTAGES OF COOLED SEMEN

1) Mare owners have a larger selection of stallions to choose from, you can access stallions from geographically distant areas.

2) Your mare can remain under your care or at a nearby breeding station during the breeding process and you can be involved in the breeding decisions if you wish.

3) The use of transported semen allows for control of disease during the breeding process.

GENERAL INFORMATION

• Cooled semen was developed as an alternative to the use of frozen semen in horses.

• Frozen semen in horses is a difficult proposition, unlike cattle where it is used extensively.

• The use of cooled semen involves collection of semen from the stallion a day of so before it will be needed by the mare owner. It is collected from the stallion by the use of an artificial vagina (AV) and a mare in heat or a phantom. It is then taken into a lab area and prepared for shipment.

  • The semen is evaluated for total volume of ejaculate, the number of sperm per ml., and the % motility.

  • The semen is then mixed with a liquid that will optimize sperm longevity and survival. This liquid protectant is called the extender.

  • Antibiotics are present in the extender and help to prevent the growth of bacteria in the sample.

• If left at room temperature (25 degrees centigrade) the extended semen would survive for only a few hours, however if the sample is correctly cooled to 4 degrees centigrade the semen can maintain it’s fertility for 48 hours with most stallions and longer with some stallions (72 hrs).

• This preservation of semen through slow cooling allows for the shipment of the semen to distant locations.

• The cooling rate of semen during preparation seems to be the most critical factor in the quality of the sample. Semen needs to be cooled from 37 degrees C to 5 degrees C at a specific rate. Cooling too quickly will significantly damage the semen.

• Once cooled to 5 degrees the container must be able to hold this temperature for 48 hours.

This process of semen preparation and cooling for shipment has been greatly enhanced by the development of the Equitainer, a commercial cooling and shipping device. There have been other less expensive products on the market, however none can match Equitainer’s cooling rates and maintenance of 5 degree centigrade temperature for the desired 48 hours. The container is lightweight and durable for airline shipment. It is quickly recognized by airport security personnel and is not often held up for security reasons during transit.

Team Work is Required For a Successful Pregnancy

• Timing is everything in the breeding business and it is especially important when using cooled shipped semen. For the timing to work correctly there must be good communication between the mare owner, the veterinarian and the stallion manager. For everything to go smoothly several things must happen:

1) The mare must come into heat

2) The time of ovulation must be accurately predicted

3) Semen must be ordered by the mare manager and shipped by the stallion manager

4) Semen must arrive in good condition & in a timely manner.

5) Mare must be inseminated prior to ovulation

• The main links in the chain are

1) The veterinarian

2) The stallion manager

3) The mare owner or manager

4) The mare

5) The stallion

6) The transporter.

Breakdown in communication or performance of an individual’s responsibility anywhere along the chain can result in failure.

 

COMMON PROBLEMS THAT MAY OCCUR

• The mare will not cooperate; early in the spring mares are unreliable with their heat cycles and may not come in heat or not ovulate on schedule.

• For one reason or another the semen does not get collected

• Shipments can get lost

• Semen does not survive the trip

Each failure is expensive so it is best to be organized and rely on the veterinarian before ordering a shipment of semen.

Frequent internal examinations of the mare by the veterinarian allow for an accurate estimation of when ovulation should occur and is essential in the correct timing of a shipment.

The Normal Sequence of Events When Breeding With Cooled Semen

1) Choose stallion and contact stallion manager well in advance of expected breeding date. Ask the following questions:

Costs:

How much is the stud fee?

What are the charges for shipped semen?

How many shipments does the initial charge cover?

What are the charges for subsequent shipments?

 

 

Collection/shipping Procedure:

Have you shipped semen from this stallion before?

What is his conception rate for shipped semen?

Is a veterinarian involved in the process?

Is an Equitainer used for shipping?

How many doses per shipment?

Timing:

Will you collect on demand or is collection limited to certain days of the week?

Can we order by a certain time of day and have semen delivered to our mare the next day?

Can you ship by air cargo if needed?

2) Mare Management

• For the mare to get pregnant we must inseminate her with viable semen just prior to ovulation. This is not as easy as it sounds. Mares are notoriously unreliable, especially early in the spring.

• The best system is daily teasing with a stallion, but this is not often possible is the back yard.

• The next best thing to a willing stallion is a willing veterinarian. Examination of the mare by the veterinarian is the first step in determining when to begin breeding..

• A good rule of thumb is: most mares do not ovulate during the winter months and the first ovulation of the year usually occurs in late March. So, beginning in February is usually not productive.

• The veterinarian should see the mare in March and determine where she is in her cycle. Once that has been determined, plans can be made.

• The hormones that are available to control the onset of heat and ovulation can be discussed at this time. Much of the stigma of using hormones to breed horses has been removed.

• These drugs are very effective and safe. They often make the difference between success and failure.

When Do You Order Semen?

• At the first sign of heat the mare should be visited by a veterinarian daily and examined.

• An internal examination of the ovaries will help determine when semen should be ordered.

The mare’s reproductive tract is examined for changes that indicate ovulation is imminent. These changes are best determined with ultrasound. Changes that indicate impending ovulation include:

• Follicular enlargement

• Changes in the character of uterine folds

This close monitoring is essential, because accurate prediction of ovulation is the most difficult part of the entire procedure. The semen needs to be delivered into the mare’s uterus just prior to ovulation. If the mare ovulates before insemination she will probably not conceive. If she waits 12 hours longer than expected to ovulate, another shipment will be needed.

• Once ovulation time has been predicted, the semen is ordered early in the day and the mare is given a shot that will help insure ovulation the following evening.

• As soon as the semen arrives the following day it is placed in the mare with the use of all plastic equipment. A long narrow straw (pipette) is attached to a syringe; the syringe should not contain a rubber plunger as rubber has been shown to be toxic to some spermatozoa.

• The semen is then drawn into the syringe barrel.

• It is placed directly into the uterus through the cervix. It is not warmed first or manipulated in any manner.

• After insemination is complete the remaining semen is examined for motility. It is best to warm the sample to 37 degrees centigrade prior to examination with a microscope in order to get an accurate reading.

• With this approach the mare typically ovulates the evening of the insemination or early the following morning.

• The mare should be checked the following morning to be sure ovulation has occurred. She should be checked prior to the deadline for ordering another shipment just in case she hasn’t ovulated and another shipment is needed.

• She will need to be bred every 48 hours until she ovulates. It is easy to see that it can get quite expensive if the mare does not ovulate on schedule.

• Once she has ovulated she should be checked within 12-24 hrs. for uterine discharge that needs treatment and an appointment should be made for a pregnancy check 14-15 days post ovulation.

This procedure can sound difficult and at times impossible to coordinate, but surprisingly most mares become pregnant on one shipment. Patience, communication and expertise are essential for a favorable outcome.

SUMMARY:

Advantages of Cooled Semen:

• Access to top stallion without concerns about location

• No shipping the mare long distances is required

Disadvantages:

• Timing is essential

• Expertise at both geographical locations is required

• Can become expensive if things don’t go as expected

FROZEN SEMEN

 

INTRODUCTION:

• Frozen Semen for artificial insemination (FAI ) has been used in dairy cattle successfully for years.

• However it historically has suffered a slow acceptance in the horse industry due to breed association restrictions and poor pregnancy rates early in its development.

• The protective action of glycerol in the freezing of semen was discovered by accident in 1949.

• Since then most of the research and funding has been in the freezing of bull semen.

• The first successful recorded equine pregnancy using FAI was not until 1975.

• FAI has been used extensively in other parts of the world in recent years. China inseminated 110,000 mares between 1980 and 1985 and claimed a 68% pregnancy rate.

ADVANTAGES OF FAI

• Economics

  • It is cheaper to ship frozen semen across country than it is to ship a mare.

  • Decrease cost of mare care by keeping the mare at home

• There is less separation anxiety for owner.

• There is less stress and exposure of the foal to disease when he stays at home.

• A stallion can continue to be used for competition during the breeding season or if he becomes injured or ill, his breeding season can continue through the use of FAI.

• Semen can be stored indefinitely for future use.

• The differences in breeding season between the northern and southern hemispheres would not be a

problem.

• The use of genetically inferior stallions should decrease.

• Interest in breeding and raising horses should increase with the access to superior stallions that FAI provides.

DISADVANTAGES OF FAI

• Not all stallions are good candidates for FAI, approximately only 30% of randomly tested stallions have good pregnancy rates with frozen semen.

• Poor pregnancy rates are still a problem.

• Some breeders are concerned that the gene pool will be decreased by many mares being bred to a selected few stallions. For most stallions, the average amount of mares that can be bred in a year totals only 200-300 with FAI. There doesn't appear to be great danger of the gene pool shrinking and in fact FAI may expand the available gene pool by making overseas stallions available.

• The income of some stallion owners will decrease.

• Stud fees may decline. Some mare owners may consider this an advantage. The stud fees will not drop as dramatically as with bull semen because of the high cost of collecting, processing and storing equine semen. The cost of collecting and preparing enough semen for one pregnancy is approx $150.00.

• Errors can be made in the identification of the offspring from frozen semen. However, the frozen semen straws are clearly marked and the stallion is indicated on each straw. The identity of the foal and the integrity of the pedigree are determined by the breeder, not the method of breeding. If there are questions the parentage can be confirmed by blood tests.

STALLION CONSIDERATIONS / SEMEN QUALITY

• The stallion must be physically able and trained to use the artificial vagina for collection of semen.

• It is also beneficial if he is trained to the phantom for easier collection.

• The semen quality after thawing will vary between stallions:

- 30% of randomly tested stallions will have 80 % of the pre freezing motility.

- 30% of randomly tested stallions will have 50% of their pre freezing motility.

• Post thaw motility can vary between ejaculates from same stallion.

• Good post thaw motility doesn't insure good fertility. Cold shock during freezing can damage the

spermatozoa's membrane structures and interfere with fertilization.

• Semen motility is determined by microscopic exam and is notoriously imprecise. Studies have shown that visual evaluation of semen motility tends to over estimate percent semen motility. The most accurate means of evaluating equine semen motility is the use of computer programs.

On average, 35% of stallions are classified as good prospects for frozen semen on basis of

1. Pre freezing motility > 60%

2. >70% of spermatozoa are morphologically normal.

3. >30% post thaw motility

4. Some spermatozoa activity for 120 hr. post thaw, stored at 1 degree Cent.

• 25% of stallions are classified as average candidates for freezing semen

• 40% of stallions are classified as poor candidates for freezing semen.

• Stallions rated good by this method also tended to be more consistent between ejaculates, producing acceptable post thaw samples in 70% of the ejaculates, whereas average rated stallions produced acceptable samples from only 50% of the ejaculates

An acceptable semen sample should have 35% post thaw motility and 200 million progressively motile spermatozoa.

PREGNANCY RATES

There are many conflicting reports of pregnancy rates obtained with FAI. The reports list if the mare got pregnant or not, however this is not always an accurate assessment of the stallion or the breeding method being studied. There are other considerations such as:

1. How many cycles was the mare bred?

2. What was the fertility status of the mares used in the study?

3. How many spermatozoa per insemination dose?

4. How close to ovulation was the mare inseminated?

On average, a good freezing stallion should achieve about 60% of his live breeding pregnancy rate when frozen semen is used, i.e. If a stallion has an 80% fertility rate on one cycle with live cover and he is a good freezing stallion he should get 48% of the mares bred with frozen semen on the first cycle.

Stallions can vary in pregnancy rates between ejaculates. Pregnancy rates for one stallion can range from 8% to 65% depending on which ejaculate is used.

The average pregnancy rate for one cycle of breeding is approximately 25-30% and 45-50% for the entire breeding season.

TIMING OF INSEMINATION

• Better results when insemination occurs close to ovulation. T

• The freeze thaw cycle damages the membrane of the spermatozoa, causing partial capacitation and an inability to attach and store viable sperm cells at the caudal isthmus portion of the oviduct.

• Frozen semen typically has short livability...6-8 hours

• Pregnancy rate drops dramatically when insemination occurs >24 hours of ovulation

• The mare should be inseminated within 12 hr pre and post ovulation.

 

 

EARLY EMBRYONIC LOSS

• Some studies indicate a higher incidence of early abortion when frozen semen is used.

• Normal loss rate is approx. 15 %.

• Loss rate with frozen semen is reported to be 21%.

PRE BREEDING CONSIDERATIONS

When selecting a mare to breed with frozen semen, the following factors should be considered:

1. Age - mares > 12 years old suffer a significant decrease in fertility.

2. Breeding history - mares that have been previously diagnosed with uterine pathology are

poor candidates.

3. Mares with foals have a slightly higher success rate than maiden mares.

Once a mare has been selected as a candidate for FAI a pre breeding exam should be done. Special consideration should be given to:

1. Vulvar conformation - poor conformation will predispose to infection and infertility or abortion.

2. Ultra sound exam of ovaries/uterus/cervix checking for anatomical abnormalities, uterine tone, cervical tone, and ovarian activity.

3. Vaginal exam- checking for urine pooling, cervical scars, cervical discharge

4. Uterine culture / cytology

5. Biopsy of uterine mucosa may be helpful if there are some questionable findings or history.

6. Ultra sound exam of ovaries and uterus to look for ovarian abnormalities, uterine cysts or fluid in uterus.

BREEDING CONSIDERATIONS

• Strictly adhere to instructions for handling semen supplied by stallion owner.

• Estimation of time of ovulation requires rectal exam done manually or with an ultra sound.

• Signs of impending ovulation are:

  • Increased heat score,

  • Softening and open cervix,

  • Uterine folds / follicle. On ultra sound, the follicle reaches maximum size (43- 47 mm) and becomes distorted in outline from spherical to irregular and the uterine folds change from the cartwheel like in appearance with dark tips seen in mid heat to uterine folds that are less edematous.

Equipment needed for actual insemination with frozen semen:

1. Sterile sleeves

2. Non -spermicidal water base lube

3. Haver Lockhart AI pipettes

4. Air Tite syringes

5. Water bath (usually 37.5 degree centigrade)

6. Forceps for removal of straw from tank

7. Liquid nitrogen tank

8) Microscope

• Most frozen semen is packaged in .5 ml PVC plastic straws sealed on each end.

• Semen is removed from the storage tank with forceps and placed in the water bath. It is thawed at a specific temperature and for a specified time as spelled out in the instructions accompanying the semen. BEWARE; rarely a straw can explode when it enters the water bath, sending plastic shrapnel through the air.

• Complete the insemination procedure by opening straw and depositing semen in syringe barrel.

• Post-breeding reactions are common due to the lack of seminal plasma in the semen sample.

Seminal plasma is removed prior to freezing and the sperm are re suspended in extender. Seminal plasma is a natural immunosuppressant; it limits the mare’s response in the uterus to the foreign protein of the spermatozoa. Without the seminal plasma the uterus reacts with massive amounts of fluid, protein and WBC production to help eliminate the foreign protein of the spermatozoa.

• These reactions are often severe enough to interfere with fertility if not addressed by the attending veterinarian with uterine clearance techniques such as lavage and oxytocin injection with or without PGF injections.

 

 

 

FUTURE OF FROZEN SEMEN

Selection of good freezing stallions will result in slowly increasing pregnancy rates.

Improved technique and personnel will result in increased pregnancy rates.

 

LOW DOSE INSEMINATION TECHNIQUES

INTRODUCTION

• To obtain acceptable pregnancy rates, the minimum recommended number of spermatozoa is:

  • 300 million progressively motile spermatozoa for fresh semen

  • 200 million progressively motile spermatozoa for frozen semen

  • 500 million progressively motile spermatozoa for shipped cooled semen

• Insemination with less than 100 million progressively forward spermatozoa results in unsatisfactory pregnancy rates.

• Interest in low dose insemination techniques results from:

  • The advent of fluorescence activated cell separation technology that can be used to sort X and Y-chromosomes. Once sorted, low numbers of spermatozoa are available for insemination and the sex of the foal can be chosen at the time of breeding.

  • The use of epididymal spermatozoa harvested after death or from stallions with occluded ducts.

  • Improve fertility of sub fertile stallions and mares.

  • Lower doses of frozen semen.

METHODS

• Rectally guided deep uterine insemination

• Hysteroscopic, using endoscope to visualize the opening of the oviduct in the uterus and target it for deposition of semen.

RESULTS

Pregnancies can be consistently obtained using as little as 1 million spermatazoa

Higher pregnancy rates resulted when using hysteroscopic insemination over conventional insemination using less than 3 million motile sperm from frozen thawed semen.

Pregnancy rates are similar between deep uterine and hysteroscopic insemination techniques when using 5 million motile sperm per dose.

• Hysteroscopic insemination is the most useful when using very small doses, such as sexed semen or when very poor motility exists.

 

EMBRYO TRANSFER (ET)

Embryo transfer is the removal of an embryo from a donor mare and placing it in the uterus of a recipient mare. The recipient mare carries the pregnancy and delivers the foal as if it was her own. The foal retains the genes of the donor mare and the stallion.

• ET was first described in horses in 1972

• It has been available commercially since the 1980’s

• Prior to 2002 the use of ET was limited by breed regulations that restricted the registration of foals from individual mares to one per year. Subsequent to a pending lawsuit, the AQHA removed restrictions and allowed the registration of multiple foals from a single mare per year.

Traditionally ET has been used in older mares that fail to get pregnant or fail to carry a pregnancy to term. This limits the technology because older mares and infertile mares are less likely to donate embryos than reproductively healthier younger mares.

 

More recently ET has been used in younger mares to expand their progeny and allow them to continue their performance career.

 

ET is being used in conjunction with other assisted reproduction techniques such as cooled semen, frozen semen, Intracytoplasmic sperm injection and Oocyte transfer.

EMBRYO RECOVERY

Currently, most clients have their mares bred locally with shipped semen and 7 days later the embryo is recovered from the donor mare, packaged and stored in an Equitainer and then shipped to a large embryo transfer facility where it is placed in a recipient mare.

• Embryos are collected from donor mares on day 6,7 or 8.

• Day 6 embryos are smaller and harder to harvest.

• Day 8 embryos are the largest size that can comfortably fit into a pipette for transfer.

• Method:

  • A catheter is introduced through the cervix, once in position the cuff of the catheter is inflated with air and the catheter is then drawn back against the internal opening of the cervix to assure a tight seal.

  • A buffered solution (Dulbeccos phosphate buffered saline) into the uterus, 1-2 liters at a time, and recovered by gravity through a 75 micron filter.

  • The procedure is repeated at least 3 times, but often times up to 6 times.

  • Embryo recovery rates per flush:

    • 31% on first 3 liters

    • 15% on subsequent 2 liter flushes

  • The filtered media is placed in a search dish and examined under magnification (7x-15x magnification with stereo dissection microscope)

  • Once located the embryo is washed, graded and packaged in a straw for immediate transfer into the recipient mare or placement in cooled storage for shipping.

• Preferred Recipient Mares:

  • Maiden mares or young mares that have had 1 or 2 foals are preferred.

  • Quiet and well handled recipient mares

    • 1000-1200lb

    • 3-10 years old

    • Halter broke

• Typically the embryo is shipped on an airplane to an embryo transfer center where many mares are kept. Usually the embryo can be placed into a mare that spontaneously ovulated on the same day as the donor mare.

• Where large numbers of recipient mares are not available synchronization of ovulation can be provided by hormonal therapy. A minimum of 2 mares is required per donor mare. Recipient mares that have ovulated 1-day prior or up to 3 days after the donor mare are candidates.

Currently most transfers are done nonsurgically.

Success rates of 75% per embryo transferred are expected with nonsurgical transfer

There is no higher rate of embryonic loss with ET than with leaving the embryo in the donor.

 

EMBRYO FREEZING

• Frozen embryo technology lagged behind other species and other equine assisted technologies

• Probably due to the inability to repeatedly harvest multiple embryos in the horse, and breed association restrictions on the transferring frozen embryos.

• Advantages include:

  • Embryos can be stored indefinitely

  • Important genetic lines can be preserved indefinitely

  • Frozen embryos can be held until a recipient mare is available, negating the need for multiple recipient mares that are synchronized.

  • Embryos can be shipped inside and outside our borders at our convenience without regard to matching of recipient cycles.

• Success rates are higher (70%) when smaller embryos are used, day 6.

 

SUPEROVULATION

• Producing more than one ovulation per heat cycle

• Advantages:

  • Collection of multiple embryos per collection

  • Improving pregnancy rates per breeding /embryo recovery attempt

• Problems:

  • Mares respond inconsistently to superovulation treatments

  • Lack of availability of commercial superovulatory drugs

  • Considerable cost of superovulation

  • Possible lowered viability of multiple embryos

  • Mares are very refractory to some drugs that work well in other species

• Treatments tried:

  • GnRH: shown to ineffective in mares during the normal breeding season

  • Equine Pituitary Extract

    • Obtained from pituitaries from slaughtered horses

    • Crude extract

    • Contains 10% LH and 5% FSH

    • Has been shown to effectively induce multiple ovulations in treated mares

    • 2-4 ovulations per cycle, still lower than obtained in other species

    • It appears there are a reduced number of embryos per ovulation using this drug.

  • Porcine FSH (follicle stimulating hormone)

    • Porcine origin FSH

    • 1.7 ovulations per cycle

  • Equine FSH

    • E FSH: a recently released commercial product (Bioniche Animal Health)

    • Useful in increasing ovulations per cycle and embryos recovered.

    • The average number of embryos recovered in treated mares was 2

 

ESTROUS (HEAT) SUPPRESSION IN THE MARE

 

When mares misbehave or behave in ways contrary to the owner’s wishes the reason is often felt to be estrous cycle related.

Common names used for this behavior include:

• Marish behavior

• Moody

• Feisty

• Pissy mare behavior

• Mare madness

However, these behaviors often are not the result of cyclic activity.

Most problematic mare type behaviors are the result of:

• Submissive behavior

• Urogenital discomfort

• Stallion like behavior

It is the job of the veterinarian to rule out these other causes of problematic behavior. Some common causes of these behaviors include:

• Ovarian tumors

• Pneumovagina

• Uterine infection

• Vaginitis

• Bladder infection

Common Complaints of Estrous Related Behavior Problems:

• Intense behavioral signs of heat that prevent training and performance

• Less cooperative

• Inattentive

Most commonly request for estrous suppression come from trainers and owners of mares engaged in some sort of training or performance.

 

METHODS OF SUPPRESSION OF ESTROUS

HORMONAL

MARBLE

SURGICAL

MMUNOLOGIC

HORMONAL

Regumate

• Synthetic progesterone
• Given orally daily
• Highly effective for suppressing estrous for the duration of treatment
• Mares come back into heat when drug is discontinued
• Safe for long term use if mare is reproductively healthy
• Contraindicated for use in mares with uterine inflammation

Disadvantages:

• Messy
• Expense
• Inconvenient daily dosing
• Human health risk

 

Progesterone in Oil

Requires daily injections intra muscularly

Highly effective

Muscle soreness is a complication

 

Medroxyprogesterone Acetate

• Depo-Provera, a human contraceptive

• low to no efficacy in the horse

• Has not been evaluated for use in horses

• Wide variety of recommended doses

• Wide variety of therapeutic responses

 

 

Hydroxyprogesterone Caproate

• Synthetic progesterone

• Has a very low binding for equine progesterone receptors

• Low efficacy in the horse

• Wide range of reported doses and a wide range of reported duration of activity

• It is reported to have a very poor ability to suppress estrous behavior in the mare.

 

 

Cattle Implants

• Progestin containing implants that are designed for use in food animal to increase weight gain

• Synovex is the most widely used

• Once implanted under the skin the dose is slowly absorbed over several months

• Scientific controlled experiments showed no efficacy for suppressing estrous in mares at 10x the recommended dose.

• In spite of this evidence many veterinarians and horse owners/trainers continue to recommend its use.

Ovuplant

• Deslorelin

• Developed as a ovulation induction agent for mares

• GnRH analogue

• Implanting a double dose of Ovuplant will suspend estrous in most mares for 30 days or more

• Work best in spring and summer

• May be repeated as needed.

Oxytocin

• IM injection of 60 units Oxytocin twice daily on days 7 & 14 post ovulation blocked luteolysis and prevented mares from coming back into heat in 100% of mares tested for at least 30 days.
• Requires multiple ultrasound exams

 

 

MARBLE PLACEMENT IN THE UTERUS

• Placing a glass marble in the mare’s uterus will suppress estrous in some mares

• Theoretically suppresses estrous by extending the luteal phase of the cycle

• Developed by a Dutch veterinarian that claimed success rates of 75%

• Recent studies proved only a 40% success rate

• When effective the marble will suppress estrous for up to 90days.

• Protocol:

  • Evaluate the mare’s reproductive health

  • A sterile 35mm diameter marble is placed in the uterus at the end of estrous within 24 hr post ovulation through the open cervix.

  • Marble must be removed from the uterus, some times difficult in mares with pendulous uteri.

IMMUNOLOGIC METHODS

GnRH Immunization

• Immunization against GnRH will suppress the hormones LH and FSH causing immune mediated estrous suppression
• Approved for use in Australia but not US
• 2 injections required one month apart
• 98% of vaccinated mares ceased estrous within 4 wk of the second vaccination and ceased cycling for the remainder of the breeding season
• 90% of the treated mares returned to estrous behavior the following season and had normal pregnancy rates when bred.

 

INFLUENCING THE SEX OF OFFSPRING

 

Sexing embryos by staining is possible but it is time consuming and reduces the viability of some embryos

Sexing embryos by biopsy, using just a few cells from the embryo and employing PCR, the sex of the embryo can be determined.

Equine sperm sexing is possible using flow cytometry, however only a small number of sex-selected spermatozoa are produced (150,000) and low dose insemination techniques are required such as ICSI and hysteroscopic techniques.

 

INTRACYTOPLASMIC SPERM INJECTION (ICSI)

• ICSI is the injection of a single sperm into a mature oocyte (eggs) in the laboratory using micromanipulation techniques.

• Invitro fertilization (IVF) is successful in other species but not the horse.

• ICSI provides a means of overcoming the problems of IVF in horses.

• Clinical use of this technology provides a means of producing foals from sub fertile mares and stallions and assists in rescuing the fertility of aged mares and stallions.

• ICSI employs ovum pick up (OPU) of mature oocytes (eggs) from the donor mares by follicle aspiration.

• OPU can also harvest immature oocytes and those eggs can be cultured in the lab until they become mature oocytes (metaphase ll).

• The mature oocytes are then injected with a single sperm cell using micromanipulation techniques.

• The resulting fertilized egg is cultured in the lab until it reaches the expanded blastocyst stage (day 6,7,8, or 9)

• The embryo can then be transferred non-surgically to a recipient mare (preferably 5 days post ovulation) or frozen for use later.

RESULTS

A group in Italy (Silvia Colleoni,PhD;Sandro Barbacini,DVM*,etal) has reported the following results

808 follicles were aspirated and 404 oocytes recovered

66% (266) of these were mature (metaphase ll) and were fertilized by ICSI

40 blastocysts were obtained after culture in the lab, of which 18 were non-surgically transferred into recipient mares.

Of the 18 transfers 15 resulted in pregnancy

5 of these pregnancies were lost before 60 days.

A group at Colorado State University (Elaine M.Carnevale,DVM,MS,PhD;JoAnne Stokes,BS;

Edward L.Squires,PhD,Diplomate ACT etal) has reported the following results:

• From 91 normal oocytes, after ICSI, 62 (68%)cleaved into at least two cells.

• Embryos were surgically transferred into the oviducts of recipient mares 34 hr after ICSI

• After 60 days of gestation, 31% remained pregnant.

CONCLUSIONS

• The loss of fertility associated with aged oocytes can be overcome with ICSI

• Poor semen quality does not affect the production of embryos using this technique

• There is no effect of season on the production of embryos using this technology

• The techniques of oocyte harvesting (OPU) and blastocyst production appear safe.