17/09/2026
Colostrum – The immune basis for early life
It is imperative that a newly born foal receives colostrum milk as soon as possible to provide energy, protein and water, as well as essential antibody protection against disease. Colostrum (first milk) provides immunoglobulins or antibodies that are concentrated into a mare’s milk during the 10-14 days prior to foaling. The transfer of circulating antibodies to the unborn foal direct from the mare’s blood is prevented by the numerous layers of the placental barrier during pregnancy. Only low levels of antibodies are present in the foal’s blood at birth and intake of colostrum is essential to provide immunity against common diseases during the first few weeks of life.
It is most important that all newborn foals receive adequate colostrum within 8 – 12 hours after birth. A healthy, active newborn foal weighing 50-55 kg at birth, will suckle between 2 – 3 litres of colostrum during the first 12 hours of life.
A foal which does not receive adequate colostrum or antibody cover during its first 16-18 hours of life, as colostrum absorption shuts down after this time, has a higher risk of failure to thrive and may succumb to infectious disease. Many of these foals develop persistent diarrhoea or have issues with their growth and development.
Secretion of Colostrum
Expert management and care of a newborn foal is essential to ensure that it receives adequate immunity via colostrum milk. A mare only produces colostrum for the first 2 – 3 days of lactation and the level of antibodies is highest during the first 6 – 12 hours. A less than optimum uptake of antibodies from colostrum can result from low levels in the mare’s milk, or failure to suckle or to absorb sufficient amounts of colostrum within the first 12 – 16 hours after birth. After 24 hours the long chain proteins which form the immune antibodies can no longer be absorbed, but local gut immunity is continued to be provided in the milk by IgA for up to 3 weeks.
Up to 12.4 % of mares pre-lactate, or ‘run their milk’ before foaling which is seen as thick milk dripping from the teats and splashing down the mare’s legs. If a mare runs her milk for more than 3 days before foaling, she will significantly deplete her colostrum levels of IgG and IgM, required for systemic immunity, but usually adequate IgA reserves will remain to provide gut immunity for 2-3 weeks. There is no way to prevent pre-lactation in a mare near to foaling.
If a mare bags up and starts to drip colostrum for a few days before her due date, then it is best to milk her out two or three times a day, using a carefully sanitised mare ‘breast’ pump or hand stripping after sanitation, as the colostrum accumulates and drips. Ensure strict hygiene and clean the teats with an alcohol-based hand sanitiser before stripping the colostrum. The colostrum can collected into a sanitised glass bottle or thick plastic bag, sealed and frozen to prevent it souring.
The foal can be fed using a long calf teat with a larger hole which enables the colostrum to drip out when the bottle is held upside down. Most important - do not feed water or cow’s milk to a newly born foal before it is given colostrum, as these fluids will shut down the uptake of the essential antibodies provided by the concentrated colostrum.
Aged mares over 20 years generally have lower levels of antibodies in their colostrum. A mare which foals earlier than 320 days of pregnancy may not accumulate adequate colostrum reserves to feed her foal. Between 750ml to one litre of frozen colostrum, slowly thawed in luke-warm water to prevent damage to the antibodies, is sufficient to establish foundation antibody immunity in a 50-60 kg foal.
During the first week of life, a foal suckles up to 105 times each day and stays within 1 metre of its mother for about 85 % of the time, rarely moving more than 5 metres away. The frequent intake of colostrum and milk containing IgA antibodies bathes the gut lining with protective antibodies. Frequent nursing also stimulates the mare to produce more milk to feed her foal, with daily volumes of 15 – 20 litres being produced by the peak of lactation 4 – 10 weeks after foaling.
Absorption of Colostrum
A foal which is born prematurely and survives should be able to absorb antibodies because the special intestinal transport cells are formed early in foetal development. Although a foal’s immune system can produce antibodies from 2 – 3 weeks of age, full scale response is not developed until 10 – 12 weeks of age. Therefore, the colostrum absorbed during the first 12 – 16 hours after birth must provide a temporary cover against common diseases over this period. The low point of immune protection in a foals’ blood, especially a foal that did not receive adequate colostrum, occurs at about 5 – 6 weeks of age. A newly foaled mare produces colostrum for only 2 – 3 days, but the level of antibodies rapidly falls after 12 – 14 hours, once her foal has suckled and depleted the initial concentrated thick colostrum reserve.
Sources of Colostrum
Colostrum can be collected from another mare within 12 hours after she foals. The best choice is a good producing mare which is still secreting colostrum after she has fed her own foal. Up to 250mL of colostrum can be stripped from a newly foaled mare at hourly intervals after each time her own foal has nursed.
Although recipes for artificial colostrum are available using cow’s milk fortified with egg protein, these may provide energy and protein, but do not provide protective antibodies. In areas where major horse studs are grouped, frozen colostrum is usually available from a colostrum ‘bank’ for orphaned or colostrum deficient foals. Some horse breeders routinely collect colostrum from newly foaled mares. Colostrum can be stored frozen for 12 months without deterioration. I cases, where a day-old foal has not suckled or fed colostrum orally, hyperimmune serum is available containing concentrated antibodies administered by intravenous injection, or in a drip, to a young foal to treat what is termed ‘Failure of Passive Transfer’ or FPT. Consult your vet for advice.
