Foal Temperature Regulation

Q: I recently clipped my 1-week-old Norwegian Fjord colt as he was having a hard time with the 95-97-degree heat here in Florida. We at first thought he was really sick with a fever, but after ruling out everything else we (me, my veterinarian, other Fjord breeders, and the University of Florida vet school) felt it was the heat. His temp went up to 105 at one point, but hovered around 103-104 during the day and 102 at night. This happened when he was 3 days old and I body-clipped him the next day, as well as hosing and having him under sprinklers. After about three more days we had a cold front move in and the temps went down to 70-80 during the day and then he was very comfortable without the hosing and sprinklers.

I have done some research and discovered various opinions on when foals begin to sweat to regulate their body temperature. My most informed sources (veterinarians in Florida who have dealt with this problem before) say that foals can begin sweating from around two to six weeks. Until that time if they overheat they can only pant to cool themselves, and this is very inefficient.

My foal had a very thick, wooly coat compared to Thoroughbred and Quarter Horse foals in this area, so I believe this is something that those of us in the warmer climates need to be aware of. Any input?       Nancy

A: Your question is a very good one. As you probably now know, the normal rectal temperature for a newborn or neonatal foal is 99.5-102° F. Healthy foals are born with the ability to regulate their body temperatures, and this is controlled by the autonomic nervous system; but this system is not fully developed until the first few weeks of life. The foal’s autonomic nervous system will cause shivering and piloerection (hair standing on end) to generate and retain heat if cold, or cause sweating to cool themselves if hot via evaporative cooling.

Sick foals, however, often lose the ability to keep warm, which is why many sick foals in cooler climates can become dangerously cold (hypothermia). And as you experienced, foals in very warm temperatures can have an elevated rectal temperature when they are overheated. Newborn foals often have a fuzzy coat, so foals born into a very warm, humid environment have a disadvantage. Furthermore, just because foals can sweat, does not mean that they are good sweaters--they might only get moist around the ears or face, especially since their autonomic nervous systems might not be fully developed yet.

Especially when the humidity is high, sweating does not effectively cool the animal and you will have a horse or foal that is overheated with a greatly increased respiratory effort in an attempt, usually a futile one, to cool himself. The high moisture content in the air when it is humid does not allow foals or adults to cool themselves via evaporative cooling very well. In these situations, the best way to cool down a hot foal is to body-clip the fuzzy, heat-retaining foal coat and bathe the foal in cool water as you did. Furthermore, in hot temperatures, make sure your mare and foal have access to shade and plenty of fresh, clean water.

About the Author

Christina S. Cable, DVM, Dipl. ACVS

Christina S. Cable, DVM, Dipl. ACVS, owns Early Winter Equine in Lansing, New York. The practice focuses on primary care of mares and foals and performance horse problems.

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