His temperature, pulse and breathing in — each one placed against the resting ranges Merck, Rutgers and the University of Kentucky publish, source by source, and the point at which those sources say to call your vet. It never names what might be wrong: that is your vet’s job.
Against the published resting ranges
All inside the published ranges
How to take them
These are published ranges for a resting horse, not a diagnosis. If you are worried about him, call your vet — whatever the numbers say.
Ranges checked 2026-09-26.
Quick answer: an adult horse at rest runs a temperature of about 99 to 101 °F, a pulse of about 28 to 48 beats a minute and 8 to 14 breaths a minute. Those are Rutgers Equine Science Center’s figures. Merck’s reference tables and the University of Kentucky draw the lines a little differently, and the checker shows all three. Rutgers says that if a horse at rest has a temperature above or below 99–101 °F, you should call your veterinarian immediately. Foals run faster and warmer.
How to use it
Take whatever readings you can, and type them in. Leave out any you have not taken. Choose adult, foal or yearling, because the ranges change a lot with age. Tick “at rest” only if he has been standing quietly: excitement raises the pulse, and exercise and heat raise the breathing for a while. Each reading is then set against each source’s range, and marked inside, above or below it. Where one of the sources prints a point at which to call the vet, that line appears at the top in the source’s own words.
Three sources, three sets of lines
The published “normals” are not one number. Merck’s tables, adapted from Dukes’ Physiology of Domestic Animals, give 99.1–100.8 °F for mares and 99.0–100.6 °F for stallions. They give a resting heart rate of 28–40 and 10–14 breaths a minute. Rutgers’ fact sheet gives 99–101 °F, 28–48 beats and 8–14 breaths, give or take a breath or two. It notes that larger breeds sit at the lower end of the pulse range. The University of Kentucky’s Craig Wood gives 99.5–101.5 °F, about 32–36 beats and 8–12 breaths. So a horse with a pulse of 44 is inside Rutgers’ range and above Merck’s and Kentucky’s. The checker says exactly that, rather than choosing one.
Foals and yearlings
Kentucky gives a foal under a month a temperature of 100–102 °F, and a newborn a pulse of 80–100 and 60–80 breaths a minute. A foal a few weeks to months old has a pulse of 60–80 and 20–40 breaths. Rutgers gives a newborn’s pulse as 80–120 and a yearling’s as 40–60. Where none of the three gives a range for an age, the checker says so and does not borrow an adult’s. Kentucky also says to call your veterinarian for a newborn foal whose temperature is below 98.0 °F.
What it will not do
It will not tell you what is wrong, or that nothing is. A reading inside every range does not rule anything out, and one outside a range is not a diagnosis. That is why the only “call your vet” lines it shows are the ones the sources print. The rule on this site is the same everywhere: if you are worried about him, call your vet, whatever the numbers say.