Numbers tell the tale : immune status foals

'Tekort aan antilichamen kan ook ontstaan wanneer de merrie weinig biest heeft, biest van matige kwaliteit óf wanneer er al veel biest verloren is gegaan vóór de partus'. (Foto: Marije de Jong)

Early in the morning the assistant at our veterinary clinic Dier-N-artsen in Oosteind, Noord-Brabant, received a phone call from one of our regular clients. The night before his mare had given birth to a healthy-looking colt foal. It was a trouble-free birth and the afterbirth came within two hours. The foal quickly got to his feet and soon got the hang of suckling. But since it’s his first home-bred foal he’d rather be safe than sorry and wants the veterinarian to visit and check the foal. The appointment was booked in for later that day and so I made my way over to this address in the afternoon.

Brisk and alert foal

Once arrived we find that dam and foal have already been stabled up to facilitate our examination. First I give the almost one-day-old foal a clinical once-over: a brisk and alert foal without observations. I point out that it might be a good idea to take a blood sample. We can easily check this at the clinic for the amount of immunity (antibodies). It is important this immunity reading is high enough: a foal with low immunity is vulnerable for bacterial and/or viral infections. Foals are born without antibodies, so without immune system. They are totally dependent on the beestings from the mare to build their own defence system against diseases. Foals develop this immunity on their first day after birth, by ingesting antibodies from the beestings that are then absorbed through the intestinal wall. This is called maternal immunity (obtained via the mare). Their own immunity won’t be fully operational until they are around six months old.

Blood samples

The owner agrees to taking a blood sample and down at the clinic this is tested for the degree of immunity the foal has at that moment. It soon emerges that the amount of antibodies in the foal’s blood is insufficient; which means the immunity is low and there is a greater risk of vulnerability for infections. These foals can be treated with hyperimmune plasma to improve the level in their immune system. Hyperimmune plasma is sterile plasma collected from healthy horses with a high level of defence; so this plasma is choc-a-bloc with antibodies. I called the owner who didn’t need long to make up his mind. The owner definitely wants us to administer a sac of plasma to his foal. So a sac of plasma was defrosted and taken along on my second visit to this foal.

Plasma drip bursting with antibodies

On arrival we create a clean area in the stable and give the foal something to make him slightly drowsy so that we can make him lie down. That gives us the opportunity to administer the drip in a quiet and clean environment. Via a catheter we carefully feed the plasma drip into the blood vessel in the neck. While the plasma seeps into the foal’s body I carefully monitor the foal. The owner comes up with a few questions. ‘Why does my foal happen to have an immunity deficiency? I’m sure he has been drinking well…?’ I explain to him that a shortage of antibodies can indeed occur when foals don’t or don’t drink enough from the beestings. But the mare can also be the reason for the shortage, for example when the mare produces little or low-quality beestings or if much of the beestings was already lost before the actual birth. So it’s not always because the foal doesn’t drink enough. Looking back, the owner realises that the mare had indeed been losing quite a bit of milk before the foal was born. So that’s probably what caused it.

Sufficient immunity

When the sac of plasma is empty the catheter is removed and we help the foal get back on his feet. I arrange an appointment for the next day to take another blood sample of the foal. Usually one sac of plasma is enough, but numbers tell the tale! Fortunately by the next day the amount of antibodies of the foal has nicely increased and there is no need for another sac of plasma. The owner’s mind is put at rest and he’s happy that he had decided to stay on the safe side by letting the vet take a blood sample of his new-born foal. He would certainly do things the same way the next time because he has now learned that reduced immunity is not always only caused by foals that don’t drink enough.

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