Building Immunity

The foal’s immune system is almost a blank slate at birth; researchers are figuring out how to best protect horses as they grow.

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The foal’s immune system is almost a blank slate at birth; researchers are figuring out how to best protect horses as they grow.

The process of building immunity against disease-causing pathogens for a horse begins with a foal’s first sip of colostrum after birth. Foals are born without much protection against the world outside the uterus. The mare’s immune system develops antibodies against what she has encountered in the environment, plus what humans have vaccinated her against during her pregnancy. She passes those antibodies to the foal via the colostrum.

The maternal antibodies circulating in the foal’s bloodstream gradually diminish as the foal gets older. Fortunately, as the foal ages its own immune system begins to mature and the foal begins producing his own antibodies. Researchers have sought to learn at what point in a young horse’s life vaccinations against various diseases will be most beneficial, and they’ve tried to determine what other steps might be taken to enhance the immune system.

These are not easy questions to answer. Yes, there are sophisticated vaccines on the market today that help build immunity against certain pathogens. But in some cases, if the vaccines are given too early, the maternal antibodies can conflict with the vaccination’s protective properties and prevent the vaccine from protecting the young horse fully

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Les Sellnow was a prolific freelance writer based near Riverton, Wyoming. He specialized in articles on equine research, and operated a ranch where he raised horses and livestock. He authored several fiction and nonfiction books, including Understanding Equine Lameness and Understanding The Young Horse. He died in 2023.

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