Breeding Mares: Investing for Success
Whether you are new to the breeding game or a seasoned stud farm manager, the communal goal of everyone involved in equine reproduction is to get mares pregnant in as few cycles as possible. A secondary goal is often to do it as cheaply as possible, though this might be futile if it gets in the way of a successful pregnancy. Realistically, it is rare to find a mare that gets pregnant on the first cycle with no medical intervention. Veterinary medicine has advanced significantly to be at a point where we have numerous diagnostic and treatment options at our disposal to give all mares the best chance of a successful breeding and pregnancy.
The following article discusses some of the resources your veterinarian might suggest in an effort to set your mare up for the most successful season. It is imperative that you have a good working relationship and coherent discussion with your veterinary team prior to breeding season, so a plan can be made with your mares and your goals in mind.
First, let’s evaluate:
Why don’t mares get pregnant?
· Inaccurate timing of insemination
· Late ovulation
· Endometritis (infected uterus)
· Post breeding endometritis (retained fluid, infection)
· Delayed fluid clearance post breeding
· Anovulatory follicles
· Inappropriate progesterone release
· Systemic illness/immune compromise (cushings, thyroid, vitamin deficiency, etc)
· Early embryonic loss
· Genetic mismatch
This is an incomplete list, but these are the most common. The italicized statements can be identified and often corrected with veterinary intervention.
Next, let’s look at:
What are the costs involved in breeding? (aside from stallion/boarding fees)
· Ultrasound (preparation, post breeding, pregnancy)
· Uterine cytology/culture
· Uterine biopsy
· Uterine treatments – lavage, antimicrobials, oxytocin
· Various pharmaceuticals
o Ovulatory drugs
o Systemic antibiotics
There are a lot of potential costs involved! However, each of these items either provides facts about the mare or allows manipulation of her cycle that ultimately provides the absolute best chance to have a successful pregnancy as soon as possible.
Let’s evaluate the role of each of the above items:
· A visual evaluation of the reproductive tract – allows for identification of mares that are ready to be bred, mares that may need pre-breeding or post-breeding treatment, confirmation of ovulation (as timing of insemination around ovulation is vital), confirmation of pregnancy status
· Done at the same time as a rectal exam – which allows for evaluation of uterine tone (should be appropriate for breeding, pregnancy, etc)
· Teasing is helpful in regards to narrowing down the time frame when a mare might be coming into heat, but ultrasound is much more specific to timing of ovulation
· All three of these give an “on paper” evaluation of the uterus and its ability to get pregnant +/- carry a foal to term
· Cytology – tells us IF a mare is infected, or has evidence of inflammation.
· Culture – tells us WHAT a mare is infected with, and provides an appropriate treatment plan.
· Biopsy – takes a sample of the uterine lining and provides a % chance that a mare will be able to get pregnant and carry it to term
· An infected uterus will not get pregnant – antibiotics and/or antifungals are used to treat these infections just like if the horse were sick with pneumonia or another infection
· Fluid impedes embryo implantation – lavage with fluids and various drugs to decrease inflammation of the uterine lining are used to minimize this fluid and make the uterus more hospitable
· Oxytocin or prostaglandins are used to promote clearance of fluid
· Tranquilization – rectal exams come with risk to the mare (rectal tear) and veterinarian (injury). Many mares are amenable to these exams, but some are not. Tranquilization and use of smooth muscle relaxants (for the rectum) are used on mares that are unwilling to stand or for which complete evaluation of the reproductive tract is not possible without. Use of these drugs is at the discretion of the handler and veterinarian.
· Prostaglandins – (Estrumate, Lutalyse) – these drugs are used to bring mares into heat, and allows us to know approximately when they will ovulate again. This allows us to time our ultrasounds and breeding.
· Progesterone – (Regumate, P&E) – these drugs are used to keep mares out of heat (in an effort to synchronize the estrus cycle) or to help maintain a pregnancy (if the mare is not producing enough of her own).
· Ovulatory drugs – (histerelin, deslorelin) – these drugs are used to make a mare ovulate at a specific time. This allows for timed insemination and better conception rates.
· Systemic antibiotics – (SMZ, Excede, etc) – these drugs are often used in conjunction with uterine treatments to manage endometritis that is either presumed or has been identified by cytology/culture
With an understanding of the helpful tools we have to breed mares successfully, the options in regards to financially approach breeding a mare are two-fold:
1. Invest in diagnostics, pharmaceuticals, and treatments.
o Knowledge is power – treatment based on facts, not guesses
§ Less repeat treatments – decreases cost
o Fewer breeding cycles – decreases cost
o Earlier pregnancies – closer to owners desired foaling time
o Higher cost per cycle (but fewer cycles)
2. Trial and error approach
o Lower cost per cycle (but potentially more cycles)
o Treatment is based on guesses, not facts, and may be wrong
o Delayed pregnancies (later season foals)
o Failed seasons
So, the question for the mare owner is: Is your primary goal a pregnant mare as soon as possible?
If the answer is yes, then the mare’s best chance is to have diagnostics when appropriate, drugs when appropriate, and treatment when appropriate. The owner’s trust of the breeding manager and/or veterinary team is imperative – that they will make the best decisions for the mare, without unnecessary intervention or expenditures.
So, how do we set these mares up for a successful season?
The following are recommendations that attempt to do exactly that. Not every recommendation is ideal for every farm or every mare, and there are places to compromise based on feasibility and/or cost. Remember that in the long run, getting a mare pregnant on as few cycles as possible is much less expensive than having several failed cycles prior to treatment or, at the very worst, a failed season.
Mares are long day breeders, and their reproductive tract essentially sleeps until March. The only way to “wake it up” is to make the mare think the days are getting longer. It is recommended to start putting all open mares under lights 12 hours a day (12 on/12 off) starting at Thanksgiving. It should be bright enough in the darkest part of the stall to read a newspaper.
Manipulating when exactly a mare will ovulate allows for fewer ultrasounds and perfectly timed insemination. It also may allow for better scheduling of busy stallions. The recommended protocol is as follows:
· Progesterone/estradiol x10days
o Injectable P&E once OR
o Regumate daily
· Prostaglandin on day 10
o Lutalyse or Estrumate
· Ultrasound 5 days after prostaglandin
· Breed 6 days after prostaglandin (most likely)
· Cytology/culture – should be performed on any open or barren mare, or any mare that has had a failed cycle. Ideally, this should be done before breeding starts (1 month or more ahead) to allow for appropriate treatment, if necessary. Ideally, mares should be treated and retested prior to breeding.
o To get the most information to most accurately treat a mare, both tests are recommended.
o If only one test is elected, a cytology has the best chance of identifying an infected mare (though treatment will be an educated guess).
o 5 days after Lutalyse/Estrumate, or after a mare starts teasing until a 30mm follicle is present with 3+ edema (allows administration of ovulatory drugs)
o 48 hours after ovulatory drugs to confirm ovulation and evaluate for fluid
o 16 days after ovulation to confirm pregnancy and evaluate for twins
o 28 days after ovulation to confirm heartbeat
· Uterine treatments
o If infection is identified on cytology/culture
§ Ideally treatment course completed BEFORE breeding
§ Less ideal, but treatment can be timed around breeding
o If fluid is present before breeding
o If fluid is present after breeding
o Progesterone (Regumate) – at 5 days post breeding for any mare that has had problems in the past, is on a 2nd (+) cycle, or who was treated prior to breeding. Progesterone levels can be pulled at the pregnancy check to determine the need to continue.
Specific groups of mares
· Open/barren mares
o Cytology/culture should be done BEFORE breeding begins, with treatment and retesting BEFORE breeding begins
o Mares with a history of endometritis – consider SMZ starting at the time of lutalyse through breeding
o Regumate starting day 5 after breeding
· Foaling mares
o Settle at 24 hours post foaling – decreases bacterial infection, improves involution
Other protocols might be suggested by individual veterinary teams, based on experience and personal preference.
In summary, mares that get pregnant on their first cycle with minimal intervention are few and far between. The most successful breeding managers and mare owners are the ones that utilize their veterinary team and work closely with them to set their mares up for success early on in the season. Being willing to financially invest in a mare’s breeding cycle greatly increases the chances she will get pregnant as soon as possible. Be sure to contact your veterinarian to discuss your goals for your mare this season.
Kristi Gran, DVM, DACVIM