The last few months before birth.

The foal season is well on its way. The first foals are born, but there are quite a few mares that are now in their last months.

During the first months after gestation a mare does not require more attention than any other (sport) horse. But that changes drastically from the 7th - 8th month. The feed, for example, the worming and vaccination schedules and the accommodation have to become optimal.


We have the natural inclination to protect the still unborn foal against anything that can go wrong. This often means that mares in foal are no longer exercised under saddle. However, there is no scientific reason for this.

Mares in foal (up to 9 months) can still easily be lightly to moderately exercised. It was even found that mares which were so exercised could, after giving birth, better cope with mild exercise than mares that had not been trained during their pregnancy. So if your mare, when she is, say, five months in foal, gets exhausted from a relaxed hack, you should consult your vet, for that is not normal.

It is really important to give mares in foal sufficient movement. Keeping them out in the field is without doubt a lot better than being locked up in the stable. If the horses must remain in their stables all day anyway, they should get daily exercise, either in hand, under saddle or on the horse-walker.

In conclusion: mares in foal are often better off when they are still given regular light exercise until they reach the 9th month.


In the first seven months the requirements of a mare in foal are not so different from those of other horses. Feeding them ‘for two’ in the first few months may not be wise. The mare - like any sport horse - should be kept in good physical condition, without going to extremes. A mare that is too heavy in the last few months of her pregnancy has a good chance of encountering problems when giving birth and for some time thereafter.

In the last four months of gestation the foal grows spectacularly fast and the needs of the dam grow drastically as well. That is when the feed will have to be adjusted. Since all feeds have different compositions, it is hard to give an advice in terms of kilograms. Nevertheless we can give you some general advice.

A healthy horse that is not doing any work will find all it needs for energy and protein in grass. This is still the most natural horse feed. Unfortunately, since only few fields offer herbs or a variety of grasses, there is a serious chance of developing a vitamin or mineral deficit. It is therefore necessary that they have access to salt and mineral licks. Also an additional vitamin and mineral supplement can be given. Analysis of the soil and/or the grass can provide very useful information.

Grazing in the field is sufficient in the first few months of the pregnancy. As time goes on, though, it is important to keep the mare in a good physical condition. If she is losing weight, you can already start feeding her a limited amount of broodmare nuts.

In later months the foal will claim quite a lot of room and this prevents the mare to consume very large quantities of roughage. In addition, the foal needs more vitamins, minerals, energy and protein than a mare can normally supply via roughage.

Where for most other horse we prefer slightly drier, rougher hay or grass from non-fertilized fields, we best feed the mare in foal with grass, silage or hay of very good quality. Concretely this means that, in order to provide sufficient protein and energy, the hay has to be soft and still slightly green. Silage should not be too moist and should also be soft and not too stalky.

Especially when a mare has no or only limited access to good grass, the roughage should be supplemented by a good broodmare nut. Still, roughage forms the basis of the diet (as applies to all horses). Broodmare nuts must be gradually introduced into the diet and steadily increased. It is best to feed several smaller portions.

The mare gets her energy mainly from sugars (carbohydrates) and fat.

Fat is the preferred and safe source of energy. Athletes having to run short distances mainly use sugars. Horses are not bred to run such short distances. The processing of sugars creates increased lactic acid production, with stiff and painful muscles (acidification) as a result. In addition, horses consuming high sugar contents are susceptible to muscle-, tendon problems, ulcers, colic, etc.

The broodmare nuts should therefore contain ample vegetable fat (preferably more than 5%) and few sugars. Feed that is rich in fat does, however, have a shorter lifespan, which is why most feeds from the shop have low fat contents.

To compensate this, you can add corn oil to the diet. Twice a day a half to full cup of corn oil will give the mare extra energy, several fat soluble vitamins and fatty acids. It is best to introduce this to the diet gradually, for horses are particular to the taste of fat.

The mare’s feed should contain sufficient vitamin E and selenium. Supplementing vitamin E even increases the number of anti-bodies in the colostrum. When she is thus fed, the foal will have a higher resistance against diseases.

A shortage of vitamin E and selenium are often a company policy problem. It is therefore advisable that major studfarms have the blood examined from 10-20% of the mares (or a representative number of the population) to check the level of vitamin E and selenium.

Shortages must be corrected. Be careful, though, because a surplus of selenium is also undesirable and may even have serious side-effects (loss of hair, loose hoof wall, etc.). If several horses are found to have a deficit, one should have a good look at the feed. Fresh grass is, in principle, rich in vitamin E (much more than dry hay). You will therefore not often find such a deficit in horses grazing in the field. Selenium, on the other hand, depends on the soil. In Flanders we find a growing number of selenium-poor fields.

In the last months of the pregnancy also the need for minerals is growing. Copper and zinc are essential for a normal development of the skeleton of the foal. But the fist-rule ‘a bit is good, more is better’ does not apply here. The aim is to provide the mare with sufficient minerals and trace elements without overdoing it. Most commercial feed is balanced and offers sufficient minerals for healthy skeletal growth and reduces the chances of osteochondrosis in the foal.

It is important to note that there are various relationships between all these vitamins, minerals and trace elements. One can make the other better digestible, or the other way around. Random supplements of one specific vitamin or mineral is not useful and can even be detrimental. For example, one must avoid a calcium deficit, but too much calcium in relation to phosphorus is at least as bad (chances of osteochondrosis in young foals). The calcium-phosphorus ratio is therefore at least as important as the right amount of either.

These relationships are so complex that it is not advisable to make up the feed yourself. In the long run it is better to seek the advice of a certified dietician or veterinarian. On various horse feed sites you can find programs that help you find the right feed combinations for your mare.


Mares in foal should be able to use all their energy for bringing a healthy foal into the world. The presence of worms causes decreased absorption and increased loss of nutrients. In addition, the mares can pass the worms also indirectly on to their foals.

It is therefore important to regularly worm these animals with the correct products. 

Around the time of the birth worm egg secretion suddenly explodes compared to the period before and after birth. This is called the ‘peri-parturient rise’ and is related to the level of resistance and hormonal factors. We should aim to keep this increased secretion as limited as possible. You can do this by worming the mare again 2-3 weeks before the due date.

For mares in foal we recommend that they receive ivermectin every two months and near the time of birth use moxidectin, which represses egg secretion during a minimum period of 12 weeks. Study the instruction leaflet to make sure that the product is suitable for mares in foal.


Above worming advice does not offer a perfect guarantee. It is, for example, not necessary to worm horses in a thinly populated field so intensively, especially not when there have been no changes in the horse population and the horses were well wormed before. Manure samples from all the horses there or again from a representative number (10-20%) can give an indication whether worming is necessary. For stables with problems in this field, with increased worm resistance, it may be necessary to replace ivermectin sooner by moxidectin or use another group of wormers. Such stables need to apply a very strict worming schedule (for all the horses at the same time, with the same product in the correct dose).

To do this, it is essential that you know the weight of the mare. Nothing stimulates resistance against worming more than repeatedly applying doses that are too low. Consult your veterinarian, use a measuring tape to determine the weight or find a weigh-bridge (for vehicles) nearby where you can weigh your mare.


A hobby breeder with a large field, who breeds one foal, or so, per year, needs not diverge from the normal vaccination schedule of the mare, when she is in foal. Yet it is advisable to perform the vaccination at the end of the gestation period (4-8 weeks before foaling). This will increase the level of anti-bodies in the colostrum and so better protect the foal.

In most cases this implies that the mare is vaccinated once a year against tetanus and once or twice a year against the flue and rhinopneumonia.

For bigger stables, with more ‘coming and going’ of horses, or stables that encountered rhinopneumonia or rotavirus problems before, the situation is different.

In such stables one needs to vaccinate more intensively. To prevent an abortion caused by rhinopneumonia, the mares can be vaccinated at 3, 5, 7 and 9 months. If foal diarrhoea caused by the rotavirus forms a problem in the stables, the mares should be vaccinated against the rotavirus at 8, 9 and 10 months. That way the foals are better protected after sucking the colostrum.

Needles to say, the vaccines used should be suitable for mares in foal.


Horses should naturally be in the field. This also applies to mares in foal. Keeping the mare in the stable day and night increases the chances of a “a bit of a leg” (moisture in the lower limbs), ventral oedema (moisture between the forelegs or along the entire belly), stable vices, etc. Sufficient daily exercise in the field is good to avoid or lose overweight. Fat, heavy horses encounter more problems around the foaling period.

As weather permits, a clean field is the ideal place for the mare to give birth. Danger of infection is often lower in the field than the stable. In addition, the chances that the foal is trampled are less. Contact with an older, experienced mare often has a calming effect on a mare that foals for the first time.

However, many owners prefer to have their mare foal in the stable so that they have things better in control. In that case, the stable should be large enough (6m by 4m is ideal). There should be no troughs on the floor (the foal might drown). The stable has to be thoroughly and completely cleaned and possibly disinfected before the pregnant mare is put in there. Most disinfectants, however, lose their power as soon as they get in touch with manure or straw. Disinfecting therefore only brings benefit when all the biological material has been removed. This means that all the bedding must be removed (preferably with a high-pressure hose).

The mare should be brought to the stable where she is to foal in time (at least 3-4 weeks before het due date). That gives her enough time to develop anti-bodies for the bacteria and virussen present in that stable. The foal will pick up this resistance via the colostrum and will thus be partly protected against the local villains.


A mare soon to give birth needs excellent teeth in order to be able to digest the large amounts of feed efficiently. When the chewing process is impaired, the whole digestive system will be affected from top to bottom.

Teeth should therefore be checked annually and be rasped when needed. The gestation period is not the best time for rasping. Often horses have to be lightly sedated in order for the dentist or vet to work thoroughly and safely. Unfortunately, every injection has its risks, which applies to all horses. Sedatives used during the gestation period do, amongst other things, temporarily reduce the blood circulation in the womb. This should not be a problem, but it would be a nasty twist if your mare aborts the foal the next day. The sedative may have had nothing to do with it, but the situation will make both the owner and the dentist feel very awkward.

So, ideally, one tries to avoid the use of sedatives for mares in foal. Your vet can assess the situation and decide that it is best to rasp another time or, if her her teeth are in a very bad way, take the risk to use a sedative.

Such tricky situations can be prevented by having the teeth of the broodmares checked and treated during the period that they are not in foal.

Caslick surgery:

Mares that have had Caslick surgery (in common terms: that have been sewn up) the vulva must be made wider 2 weeks before her due date, or, if they are very closely monitored, as soon as they display any signs of imminent birth-giving.

The last few weeks (and, in some cases, months) of the pregnancy are often very stressful times for the owner. Besides, everyone has his or her own advice of what best to do with a mare that is going to foal. Do not shun to win the advice of your vet so that this period will pass as smoothly as possible.

Source: Animal clinic Bosdreef


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