As the foaling season approaches, many pregnant mares are looking rotund and their owners are becoming anxious about the birth of a foal.
Most heavily pregnant mares proceed to have normal foalings and it is important owners do not panic as the big day gets closer.
The gestation period of the mare is very variable. Anywhere from 320-340 days commonly occurs. Some mares regularly carry pregnancies for more than 365 days. Hence mares must be monitored closely to spot the signs of forthcoming parturition (giving birth), such as udder development, waxing up and slackening of the pelvic ligaments.
For most of the pregnancy, mares can be managed as normal horses. In the last couple of months dietary requirements are increased. I suggest you speak to the nutritional adviser associated with your horse feed manufacturer to gain feeding advice specific for your mare.
As the mare gets close to foaling, I strongly advise the novice horse breeder works closely with a professional in this field. Your vet will be able to put you in touch with establishments which cater fully for the imminent mare, with facilities such as close circuit TV, foaling alarms and experienced staff and vets on call.
If a mare had a Caslicks suture (stitched vulva) the previous breeding season this must be opened prior to the start of foaling, otherwise tearing can arise.
The heavily pregnant mare can occasionally experience certain conditions. These include colic, blood or pus discharging from the vulva, running milk in advance of the due date and swelling under the belly. These conditions may be transient and of little concern, but may represent a risk factor for the mare or unborn foal.
Colic signs include pawing the ground, sweating, rolling, flank watching and kicking the belly. Colic can occur in any horse and frequently is due to pain originating from the gastrointestinal tract (stomach and guts). In the heavily pregnant mare colic signs can also be the result of the foetus moving excessively or more serious conditions, such as impending abortion/premature parturition or a twisted uterus.
If you notice your mare showing signs of colic phone your vet immediately. If it is possible to do so safely without placing yourself at risk, briefly glance under the mare’s tail and belly to see if any of the other signs listed in this article are also being shown. This will help us reach a speedy diagnosis and initiate any treatment.
The mammary gland (udder) usually develops over the last month of pregnancy, with most of the development occurring in the last two weeks. This, however, is very variable, especially with mai-den mares, who may not develop an udder until after giving birth.
Development of the mammary gland weeks, or even months, before the due foaling date may indicate abnormality of the placenta or foetus, for example placentitis (infection of the placenta), premature separation of the placenta, impending abortion or death of a twin in the uterus. These conditions would require prompt veterinary attention.
While ‘running milk’ is not necessarily indicative of a problem with the foetus, valuable colostrum (the antibody-rich and energy-rich first milk produced by a mare) may be lost in the days prior to foaling, leading to reduced antibodies available for the foal to fight infection and hence a lowered immunity.
Occasionally, pus or blood may be noticed on the lips of the vulva. The most common cause of a bloody discharge is due to mild haemorrhage of varicose veins in the vagina. These usually stop bleeding spontaneously or when cauterised with formal saline.
However, this is also seen when the placenta is separating prematurely. Pus on the vulva may be another sign of placentitis. These latter two conditions require veterinary intervention.
Some healthy mares in late gestation develop moderate oedema (swelling) on their lower belly and this may be quite normal. Some heavily pregnant mares, however, particularly draft horses or older mares, may suffer tears in the pre-pubic tendon or ventral abdominal muscles. Predisposing factors to this condition include a mare carrying twins or an abnormal fluid accumulation in the placenta called hydrops. If you suspect these conditions contact your vet immediately.
Around 1 per cent of equine pregnancies continue above 370 days. Most of the mares spontaneously deliver a foal of normal (or small) size and maturity. If there is no sign of distress to mare or foetus, induction of birth is not advised.
Lameness can occur in the heavily pregnant mare as a complication of the additional weight to carry and lack of exercise. Previous sports-related injuries, including osteoarthritis, might recur.
Foot abscesses are common in brood mares turned out permanently and increasing weight during pregnancy may lead to laminitis and strains within the hind limb suspensory apparatus. These result in the typical straight-hocked, slack pastern conformation which is usually accompanied with filling in the lower leg. Treatment consists of support bandaging, corrective shoeing, anti-inflammatories and restricted exercise.
The high energy demands of late pregnancy can result in a metabolic imbalance called hyperlipaemia which involves abnormally high levels of fat being mobilised in the blood. Miniature ponies and donkeys are particularly susceptible and clinical signs include depression, diarrhoea and anorexia.
The unborn foal matures and adapts for life in the outside world in the last 1 per cent of pregnancy. Hence, if it is born even a few days early it may be too weak to survive. This is a major argument against artificially inducing parturition.
Most mares give birth uneventfully to normal healthy foals. However, attendance at the foaling is strongly recommended in order to intervene should problems arise. Let your vet know when your mares are looking imminent so if there are emergency situations such as a dystocia (malpresentation) or premature separation of the placenta (‘red bag’ presentation) they are expecting the call. Communication between mare owner and vet is essential.
Rarely, a caesarean section may be required. It is worth discussing with your vet where this would be performed should it be required.
It is important to remember most pregnancies are complication-free. Regular monitoring of your mare and good communication with your vet should help to keep the stress out of this exciting time. Remember, do not panic.