Every breeding season, new broodmare owners join the ranks of seasoned breeders and find difficulty coming to terms with all the complications, disappointments, expenses and frustrations of trying to successfully breed a mare to produce a foal.

Many procedures are used to ensure mares are normal and free of disease, cycle normally, produce normal follicles, are served by a fresh, fertile stallion, conceive, have only one pregnancy and have a reasonable chance of delivering a healthy foal. These have become a necessity due to the financial pressures of high feed costs, service fees, transport costs, rising drug prices, wages, farm costs etc.

In an endeavour to help mare owners towards a better understanding, the following is an attempt to answer some of the most commonly asked questions.

At what age is a mare/filly ready to breed?

Yearlings can be bred, conceive and may even carry a foal, but in one experiment approximately 70% resorbed or aborted before full term. The fillies that carried a foal to full term and reared it failed to conceive the next season and remained smaller in size than the fillies that did not carry foals; therefore this is not to be recommended under any circumstances.

2-year-old fillies had a less traumatic experience. More carried to full term, but again many did not conceive the second time until 4 or 5 years old; still unadvisable.

3-year-old fillies, if fully grown and with normal cycles, can expect to carry foals to full term and continue breeding regularly each year.

When a mare has reached her mature size between 3 and 4 years of age, is cycling regularly and is producing good follicles, she has reached breeding age.

Should treatment be sought if a young mare is served over several heat periods but doesn't go in foal?

This is a difficult question due to a large number of variables. A young mare, served by a fertile stallion and returning for the 3rd time, should be examined not only physically, but as to whether she is used to conditions totally different to those encountered on the farm.

In young highly-strung race mares, breeding farms can be a very traumatic experience and they require calm handling and a high level of understanding and patience from the stud manager.

With 2-year-old and 3-year-old mares, failure to demonstrate a reason for lack of conception could indicate that immaturity is the more likely reason. Older mares should be more closely examined to ensure that ovulation occurs, cervical dilation occurs, the ovaries and uterus follow the normal cycle changes, there are no discharges after service and the cycle period follows a normal time span.

What is the optimum time for a mare to go in foal?

Following a centuries-old pattern of conception, mares are seasonal breeders in the time of year when daylight is lengthening and green feed is abundant. Only 40-50% of mares ovulate without assistance in September and early October. This percentage increases slowly to 100% ovulation in January and February.

The presence of spring green feed, low incidence of flies and milder midday temperatures favour the late October-November period. Maximum fertility in December/January is downgraded by high summer temperatures, flies causing irritation and restlessness in horses, burnt-off feed and the effects of high temperatures on semen quality and lack of libido.

All in all, the optimum time is when mares have shed their winter coats, are improving in condition, have access to green feed, have regular cycles, ovulate and are mated to a fertile stallion.

How much does the day length influence fertility?

Both mares and stallions require 16 hours of continuous daylight to reach maximum fertility. This can be maximised by putting mares under artificial lighting commencing from 30th of June each year.

Does the weather have any influence on fertility?

The weather has a very high bearing on fertility, both directly and indirectly - directly in as much that extremes of cold and heat suppress normal cycles and mares may cycle but not show. Cold weather is energy demanding and unless extra feed is supplied for energy and heat increment, the oestrus cycle is degraded and a lower fertility will result. Extremely high daily temperatures cause lowered stallion fertility and excessive heat and sweating cause other management problems, such as colic, which also effectively causes lower fertility.

Excessive dry weather means hand-feeding of good quality feed; if this slips in quality or freshness, then again, fertility decreases. Excessive wet weather causes management problems - mares don’t show readily, stallions do not like serving rain-soaked mares, paddocks bog up, feed quality may fall, and again fertility can be affected indirectly.

What condition should a mare be in at the beginning of the breeding season?

Every mare should have shed her winter hair coat and be in rising condition in early September. Thin mares may take too long to gain condition to cycle normally before late October. Overfat mares, which then lose condition, often produce few or no follicles, even though they may cycle, and many don’t even bother to cycle.

For best results, plan ahead. Get your mare into good condition to go through the winter and come out in the spring without any excess fat, be fed well enough to start increasing condition in August so as to shed winter hair and reach peak condition by mid-September to mid-October. This may be a month later in the southern half of Australia.

Is it a good idea to serve mares on their foal heats?

Mares that foal with normal healthy foals in a normal delivery, lose their placenta in 6-8 hours and do not show any post-natal discharges have as good a conception rate, carefully handled, as those covered on the 28-day heat (2nd heat period). Most mares are fully recovered from normal birth processes by 8-9 days post-foaling.

What longterm effect might a difficult foaling have on a mare’s future breeding chances?

Difficult foaling causes trauma to the vagina, vulva, cervix and occasionally the uterus. There can be bruising, tears, haemorrhages and infection, all of which can cause adhesions, deep-seated chronic infections, loss of tone and physical deformity, i.e. torn cervix, scarring of the vagina, urine pooling. Prolonged foaling may cause nerve damage, leading to leg paralysis, lameness or total paralysis, paralysis of the bladder with urine retention and overflow.

So it can create some gigantic problems, but many occur through lack of proper care and nursing when foaling began. Do not neglect a careful veterinary examination of all mares after a difficult foaling. This may need to be repeated as a safety check at the foal heat, or even daily if the mare is acutely ill. Often a full assessment can only be made in serious cases after a number of examinations over a short or longer period of time to allow healing processes to commence.

What is a prolapse and what are the consequences?

The most common prolapse in the mare is that of the uterus itself. It is rare for mares to have a vaginal prolapse. It can occur after abortion, after normal foaling, after difficult foaling, after retained placenta, but it most commonly occurs due to uterine irritation in low-condition mares.

A prolapse occurs when the mare’s uterus is turned inside out - like pulling a sock inside out. It can only occur when the cervix is open in the conditions stated above. It may or may not still have the placenta attached.

Usually, there are NO warning signs except that the mare is in low condition, hence poor pelvic muscle tone. Usually there is a period of prolonged serious contractions after foaling or the mare will lie with her back downhill and accidentally prolapse when expelling the placenta.

This is an emergency situation as it involves a highly vascular structure which is easily damaged by the mare and her surroundings. She may even attempt to kick at the prolapse. Shock is common if treatment is delayed.

Prompt careful attention, gentle handling, careful cleaning and replacement gives every mare a good chance of a full recovery. Most mares treated promptly and correctly will breed again. Severe, neglected or injured cases may die of shock or future infection, or develop adhesions and fail to conceive. Mares rarely prolapse the next breeding season, however extra vigilance is needed for peace of mind.

Can mares that have had a caesarean section ever carry a foal again?

Elective caesareans are uncommon, as are any other kinds of caesareans in mares but if the surgeon can elect the time of day and with a good team in the operating areas, there is usually a successful outcome for both mare and foal. The mare may not conceive that year, but usually conceives within 12 months.

However, mares in prolonged labour and in shock with dead foals are a different matter. They are difficult to save, and often have contaminated wounds after surgery caused by the dead foal and rotting placenta. This leads to chronic endometritis (scarring and deep-seated infection in the uterus and the lining of the uterus) and, often, heavy purulent discharges from the uterus occur when the mare is in season or after service.

Prolonged treatment may be successful but be prepared for heartbreak under these conditions.

Why do mares sometimes retain their placentas?

Some breeds of mares habitually retain their placentas and it may take several days or more before it is shed. They are usually quite fertile and often breed successfully year after year, with retention of the placenta more likely than not every year. These are a worry but, obviously, if they conceive each year, they are more of a nuisance than a problem.

The uterus receives chemica1 messages that foaling is about to, or is occurring; there is minute muscular contraction, shutdown of blood supply, contraction of the uterus, and a pushing off of the placenta from the uterine wall. A physiological process that is as normal as sunrise, but not as well understood.

However, any circumstance that upsets any of these sequences has the ability to cause a breakdown in the normal shedding of the placenta.

Viral-related abortion is characterised by the placenta being shed often still wrapped around the foal, whereas in abortions due to bacterial infections, physical violence, or placental damage from bacteria or fungi often the chemical messages are delayed or misdirected, and so the normal shedding process is lost.

The placenta is then lost by necrosis with resultant infection of the deep uterine glands. This can cause chronic infection, fibrosis, and deep-seated inflammatory changes that may be transient or permanent, leading to temporary infertility, or permanent sterility.

The remedy is continuous, gentle medication and correct treatment to prevent infection, secondary laminitis (or founder), endometritis and fibrosis.

What help is there for a mare that routinely aborts at a certain stage?

Firstly, it is necessary to attempt to define the cause of habitual abortion. Endometrial biopsy has proved a useful diagnostic means to at least give an indication that the uterus is normal or has a problem that is directly attributable to the loss of the foal. Conditions of fibrosis, deep-seated inflammation, and bacterial infection of the uterine glands are all possibilities - a previous abortion may sow the seeds for the next abortion by deep uterine gland infection.

So, as a diagnostic workup the mare should be examined when she is in oestrus on the 2nd or 3rd day, a cervical and uterine swab should be taken, an endometrial biopsy and probably a swab from the biopsy forceps as well.

The uterus should be scanned and, it necessary, examined internally by fibreoptiscope. A veterinary specialist in equine reproduction should carefully assess all these results.

Current research indicates that very few mares actually have a ‘real’ progesterone deficiency, however practical experience shows us that many mares have periods in their pregnancies when they are not thriving, have suffered feed setbacks, have been emotionally upset by travel or by the introduction of new mares. Implants of progesterone aid these transition periods by initiating periods of better ‘wellbeing’ due to the hormonal effects of the progesterone. The results indicate a higher foaling percentage than in non-implanted mares. These implants of 250mg progesterone are given at 4 monthly intervals.

What are the 'danger periods' for when mares abort their foals?

They are principally around 36 to 42 days, 90 to 120 days and again at about 270 days. If a mare resorbs or aborts prior to 36 days due to infection or a hostile uterine environment, there is failure to implant at or about 36 days and so she will cycle normally.

With any abortion between 36 and 120 days, the mare will not cycle if implantation has occurred at 36 days; many mares will commence to re-cycle about 2 months after the abortion.

The period between 90 and 120 days coincides with the placenta taking over from the ovaries in the production of progesterone; if infection or any other factor is affecting the placental hormone, abortion can occur at this stage.

Where circulatory problems occur due to inflammation of the placenta, this is more likely to occur when the foal is older and is making high demands for blood and nutrients from the mare; any disruption will be likely to cause abortion during the 3rd trimester. These mares may cycle once or twice but may easily lapse into winter anoestrus because of the time of the year when the abortion occurs.

What is resorption and when does it occur?

Resorption is associated with the death of the embryo within the uterus, usually between day 6 and approximately 36 days after conception. After 40 days there are significant placental membranes to be accounted for and the mare will actually abort the foal, even though this may not be an obvious happening due to the small size of the foetus.

Currently, it is held that there are changes in the uterine contents that cause foetal death. These are very complicated factors and may be related to the foetus’ failure to utilise substances as ordinary as glucose and as complex as protein, leading to embryonic death. This is an area of ongoing research and more will be learnt as the research continues.

Mares will only cycle if this occurs prior to implantations at 36 days; if implantation has occurred, then the mare will not usually have a fertile cycle until approximately 60 days later.

Can anything be done to stimulate mares that don't appear to cycle?

Mares that do not cycle should always he examined very carefully. They may be in foal!

Other less common causes are immature ovaries, complete lack of ovaries, infertile ovaries and uterus, congenital lack of reproductive organs, or a persistent or retained corpus luteum from a previous ovulation may be causing a hormonal block by continuous secretion of progesterone.

This can be diagnosed by ultrasound scan or by blood progesterone assay. All these have to be assessed before resorting to physical or chemical means of stimulation. This is NOT an area in which to give an injection and see what will happen.

Mares that cycle but don’t show are often timid and as a result may be doomed to be poor breeders. Some mares have genetically damaged ovaries and may only have a limited number of follicles in their entire lifetime and consequently have infrequent cycles, and even more infrequent ovulations.

Mares that persistently cycle and do not show may require regular palpation and ultrasound examination to determine the time of ovulation. Service then becomes essential and may be assisted by the use of oestrogenic hormone to increase the receptivity of the mare.

If a mare is aggressive, she may have an ovarian tumour. Again she should be scanned and/or blood tested for hormone levels.

Persistence, careful observations and regular examination often result in pregnancy. These are not the kind of mares for the faint-hearted and can be very expensive hobbyhorses.

What information does an ultrasound give and how early can pregnancy be detected?

The use of ultrasound examination as an aid to fertility investigation started in 1980 and has been a most useful aid in reproductive examinations.

It enables the clinician to ‘see’ the follicles and ovaries and to ‘see’ cysts in the uterus. It has made the examination for twins more accurate and has enabled the best assessment of the viability of the foetus.

The embryonic vesicle can first be seen when using a scanner at 5MH between 11 - 12 days, but at this stage cannot be 100% accurately assessed for the presence of cysts except that the embryo is freely moving. If the mare is re-examined 5-10 minutes later, the cyst will still be in the same position but the embryo will probably have moved to a different location. Re-scanning at 25 days allows the actual observation of the foetal heartbeat.

The scan also allows diagnosis of ovulation, of formation of the corpus luteum after ovulation, the presence of ovarian tumours and the number, frequency and size of uterine cysts. It can detect mares with uterine infections, the presence of fluid and pus, and of pregnancy.

It does not replace manual pregnancy testing. It only makes the diagnosis a visible one that can be ‘seen’ by the owner, stud master and veterinarian, and assessment of the foetus viability can be given at the same time.

Are there special requirements for breeding older mares?

Regular breeding mares carefully handled, should be bred regularly. They will often arrange a ‘holiday’ in their own way and time, with or without human intervention.

Mares that are 20 years old should be given every chance to continue breeding, Make sure they are regularly wormed, their teeth carefully checked and filed, and that they are maintained on a good nutritional ration, kept Caslicked and protected from sudden seasonal changes of feed and weather.

Foals of maiden mares under 4 years are smaller but not necessarily weaker than those of other older mares. Old mares that produce small, weak foals have uterine problems and will eventually also have trouble with conception.

Mares should be served as little as possible if the stallion is fertile. Repetitive service does increase the chances of conception but also increases the risk of introduction of infection, and old mares have less resistance to infection.

Do all mare require Caslick's procedure and when should it be cut open?

Caslick's operations have become more widely accepted as being part of a breeding programme rather than either an indication to a mare owner that his or her mare is not up to standard or just something else for the vet to charge. It has been scientifically proven that a mare with a sloping vulva and low pelvic brim has significantly lowered fertility compared to mares with upright vulvas and high pelvic brims.

This is affected by age and, in old mares, can cause a 50% decrease in fertility if the mare is bred without being Caslicked after service. This should be maintained constantly, whether the mare is pregnant or not.

Old mares have slacker pelvic attachments and consequently tend to aspirate air and contaminants into the vagina and uterus when they are in season, which results in a lowered fertility. Poor mares fall into the same category but often, when they regain condition, may not need Caslicking.

Young mares with sloped vaginas should also be stitched as soon as possible. Ideally, these should be avoided as breeders as they exhibit poor conformation. When a mare is sutured after breeding and becomes pregnant, she should have the repaired area opened just prior to foaling and, certainly in old mares, this should he closed as soon as practical after foaling.

What effects do uterine cysts have on fertility and what treatment is recommended?

Cysts are caused by the accumulation of secretions of glands within the uterine walls. What causes them and why, are queries still to be solved. About 6% of mares show some cysts and, in most mares, these do not interfere with pregnancy. However, if the presence of cysts causes poor contact between the developing foetus, the placenta and the mare’s uterus, then foetal death is a very real possibility. Large cysts have to be surgically removed. Thick-walled cysts seem to be permanent and, if only 1 or 2 are present, are usually ignored.

Is there a problem if a mare tests in foal but continues to cycle?

Normally, between 21 – 40 days the pregnant mares’ ovaries produce large numbers of small follicles, which go through a process of luteinization without ovulation. This is to assist in the production of progesterone from these follicles to maintain pregnancy.

Occasionally, in their process of maturity, these follicles excrete more oestrogen than can be suppressed by the mare and she ‘shows’ due to its presence.

If the pregnancy is normal and well established, the mare may show but will very vigorously resent being approached by teasers or stallions and, while an occasional mare ends up being served under these circumstances, usually the mare wins and is not served.

What should an owner do if a mare conceives twins?

Get rid of them if possible, either by reduction through crushing before 30 days, or, if between 45-55 days, by surgical removal of one twin, or by the use of prostaglandin.

Approximately 1% of mares carrying twins at 42 days will deliver live twins; 13% will deliver a single live viable foal; 86% will abort, have full term dead twins or weak non-viable single foals with a second dead foal. About 10% of all infertile mares have a history of ‘aborted twins’ or had dead twins, so allowing twins to progress to full term is a financially disastrous exercise. You may lose the mare, she may be infertile, or you may end up with a weak, undersized bent-legged foal.

But you will always find that ‘ray of sunshine’ who has had a magnificent pair of twins, both champions, but is the other risk of infertility, laminitis, no foal at all, and infertility too high a price if you are not the lucky 1%?

What is prostaglandin used for?

Prostaglandin is a hormone-like substance secreted by the body in response to cellular stimulation caused by injury, disease and physiological processes. One form is PGF2Ü. It is liberated by the uterus of normal mares if they do not conceive.

The corpus luteum (CL) is the post-ovulation product in the ovary that fills the cavity left by the ovulating follicle. The CL secretes progesterone for the maintenance of pregnancy. If pregnancy does not occur the CL must be removed, as its continued presence prevents the commencement of the next oestrus cycle. Under natural normal conditions, prostaglandin is secreted between 8 - 12 days post-ovulation. If the mare is not pregnant this removes the CL and, within 4 – 5 days, the mare’s next crop of follicles start to develop and the mare shows in season.

Prostaglandin's function is to remove the CL so the mares own natural physiological processes can develop new follicles. Follicles secrete oestrogen and it is this hormone that is responsible for the mare showing in season, and also in the maturing of the developing follicle.

You must therefore understand that prostaglandin is only the trigger to remove the CL; after that, the mare has to do the rest. It is extremely effective at removing the CL - the reason for it apparently not functioning as an agent to ‘bring a mare on’ is not because it doesn’t work, but because there are other factors which may prevent follicles developing, the mare does not cycle and so prostaglandin is incorrectly blamed for not functioning.

Proper examination before its use and, if necessary, scanning the ovary so the CL is actually seen will allow prostaglandin to work as intended.

Are there any good reasons for a aborting a foal and when can it safely be done?

The reason mares are difficult to get in foal after human intervention is related to abortion and its problems, as discussed above. It is never completely safe unless preformed before implantation has occurred.

There are very few ‘good’ reasons to abort a foal after 80 days; prior to this time, the effects are less traumatic and may be managed with slightly less risk.

All the nursing, post-operative care and drugs needed for a bad case of retained placenta have to be applied to induced abortions between 90 and 320 days.

Is it difficult to transport horse semen and is its use in AI successful?

There are two types of transportable horse semen - chilled and frozen. Chilled semen from fertile stallions remains fertile for at least 24 hours and up to 36 hours after collection and processing in highly fertile stallions. Results are excellent and equal to natural service.

There are problems, however. The mares must be inseminated on or about ovulation and the semen has to be transported by road or air, usually half way across Australia. This is usually the greatest problem - synchronizing travel arrangements, collection and the mare about to ovulate within 24 hours. It is successful but gives lots of people lots of hassles and, because of this, can be expensive.

Frozen semen. The technology is still not very good and at best it is only 40% fertile. The mare has to be palpated twice or more times daily and inseminated within 6 hours of ovulation – very frustrating, expensive and not to be recommended lightly until fertility figures improve. More research is required into the freezing of stallion semen.

Both these techniques are still unable to be legally used in thoroughbred mares.

What sort of mares benefit form embryo transfer? Is it successful?

Young high-performance mares that do not want a year off to carry a foal are ideal donors for embryo transfer (ET). The embryos are viable, the mares fertile and it is highly successful.

Many people try to use ET to salvage old mares that won’t carry a foal normally, either due to early abortion, infection etc. Well, the mare has to conceive, the semen has to pass through the lumen of the uterus, and so this has to receive a lot of attention in old mares. Provided fertilization occurs and the embryo returns to the uterus on 6th or 7th day, the uterus has to be receptive, or it kills the embryo. Or due to the old mare, the embryo is fragile and will not stand the transfer.

Success is related to the viability of the product. Young mares are likely to be very successful whereas old mares require time, treatment, and patience. There are high financial rewards if a live foal can be produced.

Is it possible to tell from a mare's size and conformation whether she will carry a foal easily?

A normal well-developed mare with good bone structure that conceives to a normal-sized stallion of good conformation rarely has trouble foaling. Over fat, under-exercised, lazy mares often are responsible for some foaling troubles.

Sires that have large foals are another problem.

Viral diseases like Akabane virus and Ross River virus have been blamed for contracted joints and excess grain feeding can cause bent-legged foals at birth.

What services do vets offer to help achieve maximum fertility?

Every reproductive practice has good services to offer, which cover entire health programmes for your breeding stock and these usually can be tailored to suit a particular need. Full and open discussion with your veterinarian BEFORE the season is a very wise move, as this sets the scene before the action begins.

Elaborate tests and apparatus are available but, unlike the medical profession, we do not have private health insurance or Medicare and these tools have to be provided either by the veterinarian or the horse farm. Consequently, where horse numbers are low, veterinarians cannot afford the luxury of expensive items like ultrasound scanners. Unfortunately, cheap models are available, but with these, while they often detect pregnancy, it may be as late as 30 - 40 days and may not he powerful enough to detect abnormalities, such as cysts, twins or uterine fluid.

A good talking relationship with your veterinarian will be to your mutual benefit.