You will need a livestock thermometer and Vaseline, and a stethoscope. Most livestock or farm supply stores carry thermometers. The easiest to use are electronic, and will beep when the temperature recorded is accurate. Any thermometer used for people can be used for a horse, but it’s helpful to have one specifically designed to be used for livestock, because they come equipped with a string to attach to the horse’s tail. This prevents the thermometer from dropping onto the ground, or from disappearing into the horse’s rectum!
You can buy a stethoscope at a medical supply store. Learn to use it on yourself. Place the earpieces into your ears, then place the pad onto your chest to listen to your heartbeat. Learn to hold the pad still, so that the pad picks up and amplifies only the heartbeat, not the sounds of sliding around, which can be distracting.
Temperature: With the horse tied up, walk toward his hindquarters on his left side (if you are right handed (Approach from the right if you are left handed), gently and firmly sliding your hand down his croup to let hem know you are there. Carefully shake the manual thermometer down (grasp it firmly—you don’t want to throw it!), or turn on the digital thermometer. Apply a little Vaseline to the tip, then insert the thermometer into the horse’s rectum two or three inches (or as far as the digital one will let you), then secure the string (if there is one) to the horse’s tail. If there is no string, hold onto the end of the thermometer. Be careful until you know your horse, and stay to the side, up close to his hindquarters. Your horse may kick, and you should be in as safe a place as possible. Time two minutes for a manual thermometer; most digital ones beep when it’s time to check. Remove the thermometer and check the temperature. If you have difficulty reading the manual one, rotate it slightly until the numbers come into view. Normal temperature for a horse is 98.5-101 degrees.
Pulse: The horse’s pulse is much slower than a human’s, so can be somewhat difficult to detect. You may do this manually by placing your fingertips on the large artery up against the inside of his jawbone near his cheek. If you can’t detect it, use the stethoscope and place it immediately behind the elbow of his front leg in front of the girth area. Count the pulse beats (each lub-dub counts as one beat) for 15 seconds, then multiply by 4 to get the rate per minute. Normal pulse rate in a horse is 28-45 beats per minute. Ponies may have a slightly higher normal pulse rate.
Respiration: Watch the horse’s flanks, counting every inhalation for 15 seconds. Multiply by 4 to get the rate per minute. Average normal respiration rate for a resting horse is 12-20 inhalations per minute, but if he is excited, it will be higher.
Take your horse’s vital signs over a number of days in different weather and temperature conditions. Establishing this normal baseline for him will make it easier for you and your vet to be able to interpret and react to variations in these values.