Farm Ireland

Wednesday 25 April 2018

Maximise care of your mare in pregnancy

Smart management of broodmares will lead to healthier offspring and to lower vet bills

Wendy Conlon

Correct management of your mare throughout her pregnancy will maximise the chances of having a healthy, live foal and a mare that is ready to go back in foal again quickly. A healthy mare and foal will mean fewer complications and lower veterinary bills, which in turn will improve the profitability of your breeding operation.

When it comes to feeding, the nutritional requirements of a broodmare do not differ from that of a non-pregnant mare until the last three months of her pregnancy.

From the eight month of pregnancy onwards, correct nutrition is essential. This is not simply a case of feeding more, the diet must be balanced and meet all the mare's nutrient requirements.

The milk of all species is low in minerals. For this reason the foal must store minerals -- including copper, zinc, manganese, selenium and iodine. These reserves are built up in the liver and will supply the foal with minerals during the most rapid period of bone growth, the first three months after birth. If the mare's diet is lacking in these minerals, the foal will be unable to build reserves and bone and joint development will be affected.

Body condition

All broodmares should have their body condition assessed regularly. Good body condition helps barren and maiden mares establish normal cycles sooner in the breeding season and results in higher conception rates. Similarly, mares in good body condition at foaling are easier to rebreed than thin mares.

Body condition can be assessed by evaluating the amount of fat deposited on the ribs, along the neck and spine, and behind the shoulder. The typical scoring system uses a one-to-nine scale, where a horse with a score of one is emaciated and nine is obese.

A horse with a condition score of five is considered to have 'moderate' body condition. Mares that enter the breeding season with a condition score below five have reduced reproductive efficiency. Therefore, the target body condition score for broodmares is at least five.

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Horses with body condition scores between five and six have ribs that can be felt easily, but are not visible. In addition, they have enough fat cover over their topline, and the loin area is relatively flat. Their necks are not thin and blend smoothly into the shoulder.

A horse with a score higher than seven has ribs that are difficult to feel and so much fat along the spine that there is a deep crease in the loin area. If the spine is visible along the loin area and the ribs are also visible, then the score would be closer to a four. If more of the bony structures are visible (eg, shoulder or hip bones are prominent) then the score would be below a four.

Although high condition scores have not been shown to negatively affect reproduction, they might increase a mare's risk of limb and hoof problems, including laminitis.

If a mare is losing body condition, it is likely that she is not getting enough of the nutrients she needs.

Even if your mares appear to be maintaining body condition but pasture is showing signs of overgrazing, it is probably time to offer forage. Any forage that is fed to horses should be free of toxic weeds, dust and mould.

Concentrate feed

The term 'concentrate' refers to a feed that is a concentrated source of calories. Common concentrates, such as oats and other cereal grains, are good sources of calories but they are low in calcium and other necessary nutrients. Commercially manufactured concentrates usually include cereal grains, but they also contain additional nutrients.

If a concentrate is formulated for a broodmare, the level of nutrient supplementation will be targeted to meet her needs. Concentrates are added when the forage portion of the diet does not provide enough calories to meet a mare's needs.

Most thoroughbred-type mares should receive five to 10 pounds of concentrate in late gestation. Mares from more thrifty breeds will usually be fed less concentrate in late gestation.

Supplement pellets (balancers) are concentrated sources of vitamins, minerals, and sometimes protein.

They are fed in small amounts (usually one to two pounds per day) when the pasture or forage provides all the calories a mare needs.

For example, if a mare can maintain a condition score of six on pasture or forage alone, then she does not need the extra calories provided by a concentrate. But she does need many of the vitamins and minerals provided in the supplement pellet and indeed the protein.

Supplement pellets are not needed if a mare is getting at least four pounds of a commercially manufactured broodmare concentrate. However, a supplement pellet can be combined with a plain cereal grain (such as oats) if an owner prefers not to use a commercially manufactured feed.


Pregnant mares should be separated from other horses on the farm, especially those which travel away from the farm, to limit transmission of diseases that potentially could have a detrimental effect on pregnancy.

It is good practice to move the mare to the environment that she will foal down in at least two weeks before her foaling date so she builds immunity or antibodies against local pathogenic organisms in that area.

These antibodies will be passed on to the newborn foal through her colostrum.


Mares in late pregnancy will generally obtain enough exercise from grazing in a pasture or walking in a paddock. Stress should be avoided as much as possible.

Routine health care

Dental care and foot care should be provided as needed.

However, it is generally recommended that annual dental examinations and procedures be performed after the mare foals and before she is covered again, in order to avoid any stress from the procedure(s) and to avoid sedation while pregnant.


Pregnant mares should only be transported when necessary, to avoid stress and the potential for injury while travelling.

The mare should be moved to the farm, stable or paddock in which she will foal down at least two weeks before her estimated foaling date so she can build up immunity to local pathogenic organisms.


Vaccination to prevent equine herpesvirus (EHV-1) abortion should be given at five, seven and nine months of pregnancy. On farms with a history of EHV-1 abortions, it may be recommended that the vaccination series against EHV-1 be initiated at the third month of pregnancy.

Pregnant mares should be vaccinated against tetanus four to six weeks prior to their due date. This will provide immunologic protection to the mare as well as increase the amount of antibodies available in the colostrum. These will be passed to the newborn foal in the colostrum and provide protection for the first six weeks of life.

If the farm has experienced problems with Rotavirus, it may be prudent to vaccinate mares at eight, nine and 10 months of pregnancy to optimise passive transfer of antibodies through the colostrum and to reduce the incidence and severity of rotavirus diarrhoea in foals.


Anthelmintics (dewormers) should be administered to pregnant mares on a routine basis, with the specific chemical component and frequency of dosing based on the exposure level, parasite load and farm management practices and in consultation with the vet.

Most dewormers are safe for use in pregnant mares. However, it is recommended that the product label be examined before administering dewormers or any other product to a pregnant mare.

Routine deworming throughout gestation will decrease the exposure of the newborn foal to parasites. It is recommended to deworm the mare approximately one month prior to her anticipated due date.

One of the first parasites a foal may encounter in its young life is the intestinal threadworm (Strongyloides westeri). Larvae of this parasite may migrate to the mammary gland of the pregnant mare and subsequently be passed through the colostrum to the foal as it nurses.

An infestation of Strongyloides westeri can cause enteritis (inflammation of the gastrointestinal tract) and diarrhoea in foals and may predispose them to other intestinal problems. Administering an ivermectin-type dewormer to the mare immediately after foaling will prevent or reduce the degree of Strongyloides westeri infection in the foal.

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