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EquineRepro@yahoogroups.com FAQ's about the non-pregnant mare

For more information about the FAQ system, or to look at FAQ's of other areas, please return to the FAQ index page.
Q1: I am looking at breeding a mare, and want to know what checks I should ask the vet for.
A: There are two categories of breeding-related examinations preformed prior to breeding. the first is the "breeding soundness examination". This examination is performed to evaluate - as the name describes - the ability of the mare to become pregnant and successfully maintain the pregnancy to term. The depth of evaluation will depend somewhat upon other factors such as the age and prior reproductive history of the mare. At the very least it should include an ultrasonic evaluation and palpation of the internal reproductive tract (vagina, cervix, uterus and ovaries) and a culture and cytology. For mares that are older or have had a poor prior breeding record, and uterine biopsy may be a valuable addition.

The second category of breeding-related examination is know as the "pre-breeding examination". This will evaluate what structures are present on the ovaries (follicles/CL's), the size of the follicles, and the prediction of timing of breeding.
Q2: My mare has been in heat for ages [var: "is always in heat / never goes out of heat"]. Is this a problem, is there anything I can do to get her out of heat, and when do I know to breed her?
A: The first thing to consider is the time of year. If it is either early or late in the breeding season, the mare may be in what is known as "transitional phase". This is present between the winter anestrus period, when the mare is not in estrus ("heat") at all, and the regular physiological breeding season. During this time frame, prolonged estrus periods are perfectly normal. If the mare is to be bred, it is important to confirm ovulation, as often during these prolonged transitional phase heats, mares do not ovulate. If the time of year is not such that transitional phase would be expected, then another possibility is that the mare is not truly in estrus, but rather demonstrating a submissive behavioural response - something that can be confirmed with the use of ultrasound or a blood-progesterone assay (either of which would indicate the presence or absence of a Corpus Luteum and therefore a recent ovulation). The use of the oral progestin RegumateTM or other forms of progestin therapy may assist in reduction of estrus-like behaviour, but it will not be universal in success in all mares. Determining when to breed a mare such as this can be difficult and often the use of ultrasound or serial palpations in necessary. Another alternative is to use the hormone combination progesterone and estradiol (P&E), which can be started at any time in cycling mares and will produce a fairly predictable timing for ovulation.
Q3: My mare won't show heat to my teaser while she's nursing, what should I do?
A: Some mares will completely "shut down" after foaling, while others will refuse to display estrus to a stallion. This is known as "lactational anestrus". The first thing to do is determine which the mare is - shut down or not displaying. This can be done with ultrasound or a blood-progesterone assay (several of either may be required). If the mare is not cycling (i.e. has shut down) then the use of GnRH and/or Domperidone may be beneficial, but a cheaper and more reliable method is to wait until the foal has been weaned! Typically such a mare will return to estrus around 3 weeks after weaning. In the event that the mare is cycling but not displaying, then serial palpations or ultrasound can determine the correct time to breed, and AI can be used. Another alternative is to use the progesterone and estradiol injectable formulation, which can be started at any stage of the cycle and will result in a predictable timing of ovulation in a high percentage of mares.
Q4: What is P&E?
A: This is "progesterone and estradiol", a hormone combination given to mares to induce cyclicity in a timely manner. The addition of the estrogen portion gives a far superior control over ovarian activity to that which is seen with progesterone (or any progestin such as RegumateTM) therapy alone. It is an injectable product, with a course of 10 daily injections giving the most reliable result. It can be started anywhere in the mare's cycle as long as she is cycling (it will not work in anestrus mares, and is unreliable in transitional phase mares), and will result in the development of a 35mm follicle by the 8th day following the end of the treatment period in 90% of treated mares. For more information, there is an article on progesterone and estradiol available at Equine-Reproduction.com (follow that link). P&E is a steroid combination and therefore a controlled substance requiring a prescription. There is no brand-name product, and it must be obtained from a compounding pharmacy - and it is essential that the compounding pharmacy used is familiar with the product and uses the correct drug combinations and amounts.
Q5: My mares need to go under a light program, how does it work? How bright do they need to be? Is the burst mode better than the 16 hours? Do I need a timer? Will it affect my stallion?
A: Artificial lighting ("phototropic stimulation") works by convincing the mare that - as the days are "longer" - spring has arrived, and it is time to start regular cyclicity. The general rule of thumb for the intensity of light required is that it should be sufficient to allow reading a newspaper anywhere in the stall in which the mare resides. Duration can be either a total of 16 hours (all artificial or natural and artificial combined and continuous - i.e. no break in between the forms), or a burst of light about 1 hour in duration somewhere between 7½ and 9½ hours after the onset of darkness. Either method - 16 hours total or the burst - will have similar results, with the onset of initial estrus being in about 60-90 days. Use of a timer is valuable but not essential, in that it allows an automatic start of lighting (although this is almost essential with the burst system that will require the lights to be turned on in the middle of the night!). With any form of lighting program, it is essential that the lights be confirmed as working, as three consecutive days of no lighting program will result in the "resetting" of the mare's clock to zero in most cases!
Q6: How effective is it to breed an old maiden mare?
A: Average pregnancy rates in mares older than 13 start to decline, but that does not mean that one should not breed such an older mare! Generally, one will need to be a little more conscious of procedures when breeding the older mare, and closer management will yield better pregnancy rates. A breeding soundness and pre-breeding evaluation is always valuable in any mare, but more so the older the mare is! It is also worth considering an "endometrial biopsy" in some of these mares as uterine condition is positively correlated to foaling rates, and older mares will tend to be more likely to have endometrial problems.
Q7: I have a barren mare, what needs to be done before I breed her?
A: As with the older mare, breeding soundness and pre-breeding examinations are recommended (see Q1 for more details).
Q8: Prostaglandin, hCG, Estradiol, Progesterone, Regumate ... How are they used?
A: Rather than discourse here in detail, we would recommend that you look at the articles available at www.Equine-Reproduction.com.
Q9: My vet says my mare has "poor reproductive conformation" and requires a "Caslick's procedure". When is this put in, when do I remove it and how do I breed my mare if she has one in?
A: Poor reproductive conformation can have a very negative impact on pregnancy establishment and maintenance as it can result in an increase in uterine pathogens and irritants. Reduction of a problem is aided by the suturing of the labial lips in a Caslick's procedure. This is best put in immediately after the last breeding takes place - the highest incidence of pregnancy loss will occur during the first 15 days following ovulation, so waiting until pregnancy check time at 15 days may already have resulted in a loss. Placement following breeding will mean that if the mare is found to be open and requires rebreeding, it may be necessary to open the Caslick's procedure, but depending upon severity, it may also be possible to breed AI or place a "breeder stitch" below the sutured section (a breeder stitch is single stitch commonly made of umbilical tape or some other heavy suture material). The Caslick's procedure will need to be opened prior to the mare foaling, and it is recommended to open it around 310 days of pregnancy. It is unlikely that the labial lips will reseal, as there are no sutures securing them together, but if this is a concern, the application of a little Vaseline to each side of the opened labia may assist. There is a detailed article discussing reproductive conformation and the Caslick's procedure available at www.Equine-Reproduction.com