Colostrum or “beestings” is the first milk produced by the mare after foaling. It contains high levels of immunoglobulins (antibodies that are produced by the immune system to combat infections). The complex structure of the placenta prevents antibody transfer from the mare to the foal during pregnancy.

It is therefore vital that the foal receives adequate colostrum immediately after birth. This ensures that the foal is protected from infection during the first few weeks of life, as its immune system develops.

These antibodies are large molecules. They must be absorbed from the intestine into the blood intact in order to be effective. This specialist ability of the gut wall to absorb the antibodies decreases from approximately 12 hours of age and is gone by the time the foal is 24 hours old. As soon as the foal is born, it is exposed to bacteria in the environment, so it is vital that protective antibodies levels are present in the bloodstream to reduce the risk of infection e.g. navel or joint ill. Once the foal has nursed after birth, the colostrum is rapidly replaced in the udder by normal milk.

Ideally all pregnancies would result in a healthy foal that is able to stand and nurse from a dam that has plenty of high quality colostrum. Unfortunately this is not always the case and some foals may need supplementation.

Mare risk factors for poor quality colostrum:

Obviously if a mare dies or suffers a serious injury during delivery, the foal will be unable to nurse. Even if the mare remains healthy and produces colostrums, the foal may not receive enough of it.

Risk factors for inadequate colostrum intake by the foal:

BANKING COLOSTRUM

Because the window of opportunity for antibody absorption by the foal is so short, the situation must be dealt with urgently. Access to a bank of frozen mare colostrum is ideal and many breeders will collect and store some colostrum each year to deal with emergencies. Colostrum can be milked off healthy mares with an adequate supply after their own foal has nursed.

When collecting colostrum, make sure that you wash your hands thoroughly and the mare’s udder and teats should also be cleaned. All containers should be spotlessly clean. This will reduce the level of bacterial contamination in the colostrum. Once collected, the colostrum should be filtered through a sieve or gauze to remove any debris and placed into clean plastic containers or bags for immediate freezing.

The date of collection and the volume of colostrum should be written on the container with a permanent marker. Do not allow the colostrum to sit out at room temperature, as this promotes bacterial growth.

Note: if a mare has previously had a jaundiced foal, or if she has tested positive for foal jaundice antibodies before foaling, her colostrum should always be discarded. It is not suitable for freezing as the harmful antibodies will survive and cause disease if fed to another foal.

QUALITY ASSESSMENT

It is a good idea to check the quality of the colostrum before freezing. Visual inspection will give some indication: ideally colostrum should be a rich yellow colour with a thick and sticky consistency. A mare colostrometer (Fig 1) or a Brix colostrum refractometer (Fig 2) can also be used to assess the antibody concentration. These instruments can be purchased from veterinary, agricultural or laboratory suppliers.

A colostrometer is a hollow glass instrument with a graduated scale on its neck. Check when purchasing that it has been calibrated specifically for horse colostrum, not that of cows. It is floated in distilled water at room temperature and a sample of the colostrum is placed within it. A reading is made at the point on the scale where it meets the surface of the water. Values of greater than 1.090 indicate high quality colostrum, ideal for freezing, 1.060-1.090 indicates acceptable antibody levels. Results of less than 1.060 indicate inadequate antibody levels. Colostrometers are fragile and the results can vary depending on the temperature of the water, the colostrum and the room air. However they are relatively cheap and easy to use.

Refractometers are slightly more expensive to buy initially but they are also more accurate, easier to use, more durable and only require a few drops of colostrum for testing. The results are read off a Brix scale, with less than 20 indicating low antibody levels, 20-22 acceptable and greater than 22 high antibody levels. Laboratory testing of colostrum is also an option but obviously this takes longer to obtain the results.

FEEDING COLOSTRUM

Frozen colostrum will keep well for up to one year. Thawing should be done slowly, either at room temperature or in a tepid water bath. Microwaves and high temperatures should be avoided, as this will damage the antibodies.

Because healthy foals nurse little and often, it is very difficult to know how much colostrum they typically drink. However one to two litres of good quality colostrum are considered to be protective. Orphan foals or those being supplemented should receive this volume within six to 12 hours of birth. Foals with a strong suck reflex that are able to stand unaided can be bottle-fed. Always hold the bottle so that the foal’s muzzle is lower than its ears and avoid teats with a large hole that the milk runs out of freely. These precautions will reduce the risk of milk entering the lungs.

Foals with a weak suck reflex and/or those that need assistance to stand should not be bottle-fed due to the high risk of milk entering the lungs. These foals should receive veterinary assistance and be tube fed until they are strong enough to nurse safely.

Once the foal is 12-24 hours old, a blood sample can be collected and analysed to check that adequate levels of antibodies have been absorbed into the bloodstream. Test kits are available that allow the results to be obtained very quickly and easily.

Results of 8g/L or higher are considered protective. If the results are lower than this, your veterinary surgeon should be consulted, as the foal may need to be placed on a course of antibiotics or receive a plasma transfusion to increase the antibody levels. There is no point giving more colostrum at this stage, as the foal’s intestine will no longer be able to absorb the antibodies and they will not reach the bloodstream.

If fresh or frozen colostrum is not available, you could consider administering a commercially available mare colostrum substitute instead. These products contain modified dried cow colostrum so they typically do not confer as strong a level of protection and the foal will be at an increased disease risk. Using fresh cow colostrum has similar drawbacks. If you find yourself in this situation, you should consult with your veterinary surgeon: a plasma transfusion may be a better option for the foal.

Ideally you won’t need to use any of this advice this breeding season and all your mares will produce healthy foals and go on to rear them uneventfully in 2014. However when it comes to bloodstock, it is always better to anticipate potential problems and be prepared!

Karen Dunne MVB, MA, CertEm (Stud Med) is a veterinary surgeon and veterinary programme director at Dundalk Institute of Technology. She is a member of the Equine Group of Veterinary Ireland

Email: hq@vetireland.ie

Telephone: 01-4577976