All horse owners should be able to take their animals’ temperatures. It can be done easily using a normal clinical thermometer, and is by far the best way of telling when a horse has an infection or may be developing a fever. Before proceeding, the thermometer must be shaken vigorously to ensure that the mercury level starts below 100° F. It should then be lubricated (with petroleum jelly or saliva), inserted into the horse’s rectum and held there for one minute. To carry out this operation, get someone else to hold the horse’s head firmly, preferably using a bridle, and stand beside the horse.

Moving quietly and talking to the horse, run your hand along the hindquarters to the root of the tail. With the left hand, pull the tail toward you to expose the anus, and then insert the thermometer. At this stage, the tail can be released while the thermometer is held in the rectum. To stop the horse from moving away sideways and pulling the thermometer out, it may be helpful to keep hold of the tail, or to hold the horse against a wall. With nervous horses, or those that try to kick, it is helpful if the person who holds the horse’s head also holds its left foreleg up. In any case, the thermometer must be held all the time it is in the horse’s rectum. If it is not, its presence may stimulate the anal sphincter and either droppings will pass and the thermometer will smash on the ground, or the anus will relax and the thermometer will disappear inside (for this reason, tying a string to the thermometer may be a good idea).

The normal temperature of a horse is 100.5° F. The temperature can vary slightly up or down by half a degree during the day, and between individuals. Foals have a slightly higher temperature than adult horses; for them, up to 101.5° F can be considered normal. Taking the temperature is often the only way of telling that a horse is ill, particularly when it is incubating an infection. Fevers and below normal temperature (as from shock) require prompt veterinary attention. You should contact a veterinarian if a horse’s temperature is above 101.5° F, or below 100° F.

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