Haemolytic Disease in Newborn Foals
feed and within 3 hours of birth foals usually sleep for 7 to 10 minutes, before standing and nursing again. Bouncy little play movements begin around 2 hours and most have organised their legs sufficiently to be able canter and gallop by 6 hours of age. By the end of the first day the normal foal will be nibbling grass, galloping and grooming itself; licking and chewing fences, tails, trees, buckets and bins and passing urine and manure. Between 1.5 and 2 minutes is spent suckling, which takes place up to 24 times a day. Normal sleep periods range from 15 to 30 minutes and occur 20 to 25 times a day. If the foal appears drowsy, excessively sleepy or is not feeding vigorously then a veterinary clinical assessment is indicated.
Any foal that goes off suck, lies around more than would be expected, becomes sleepy, has signs of colic or yellowing of the gums, must be treated urgently. Even the strongest foal will quickly deteriorate if it’s red blood cells are being destroyed. Foals are normal at birth and show normal behaviour until the destruction of red blood cells causes anaemia as soon as 6 hours after suckling. Affected foals then become lethargic and may yawn a lot. If they are exerted or excited, their respiratory rates and heart rates increase markedly and a pulse may be seen travelling in waves up the neck. The eyes and gums may be jaundiced and the urine discoloured red. Signs may appear on the first, but usually on the second day after birth. However, each case is different and if severe the foal may be found collapsed.
Whether a foal is a risk can be determined with reasonable accuracy if the blood type of the mare is known. Some studs identify high risk mares on blood type – those that are Aa- or Qa negative can be monitored during the last 2 – 3 weeks of pregnancy. The disease can then be prevented by muzzling the foal for the first 24 - 36 hours after birth so that it cannot ingest colostrum from the mare. Donor colostrum from a nonsensitised mare must be given to provide immunity. The colostrum from the dam is regularly milked for 36 hours and discarded. The ability of antibodies to be absorbed through the lining of the gut is limited to the first 24 – 36 hours after birth and ingestion of antibody after this time cannot cause the condition, so the foal can suckle normally after the danger period.
Prevention is much less taxing than treatment. Effective prevention requires knowledge of the mare’s blood type. Dr Kevin Bell at the University of Queensland Australian Equine Blood Typing Research Laboratory, has been working in this area for many years. By determining the blood type of the mare and testing her blood in late gestation, the laboratory can provide concerned owners with the information necessary to prevent the development of the disease in foals at risk. The disease is rare in maiden mares because they have not been exposed previously and have not mounted a strong immune response to other blood types. In the next 12 months, parentage testing will done using DNA analysis instead of blood typing. DNA analysis will not provide information on blood type and it will not be possible to identify high risk mares from the test. However, equine veterinarians will be able to advise on other testing procedures.
Treatment is based on veterinary examination, laboratory tests and supportive measures, such as transfusions. Do not be tempted to administer or provide any form of iron supplements to the foal – both oral and injectable preparations have been linked to death in young foals. The provision of a