More Thoughts on Taking Temperatures
I find it amazing that mammals can regulate their body temperature they way they do, despite drastic changes in the temperature of their environment. It was -30 degrees celcius this morning (welcome to Ontario in February!) as I was waiting with my daughters for the school bus, and despite the feeling that my ears were going to freeze and fall off, I'm sure my core body temperature was about the same as it was when I left the house. Body temperature regulation is a key function in mammals that is controlled by the central nervous system. The body expends a lot of energy and great effort to keep its temperature within quite a narrow range.
Increased body temperature (i.e. fever) is often a key indicator of disease, and usually, but certainly not always, infection. Other things that can cause increased body temperature include exercise (particularly during hot weather), some toxins, and sometimes cancer. Fever is a natural response to infection that can actually help the body fight infection. Unfortunately, fever can also have adverse effects on the body, particularly if it is prolonged or extreme. Different sources use slightly different ranges for the "normal" body temperature of a horse, but 37.5-38.5C (99.5 to 101.4F) is commonly used. Slight elevations can be present in healthy horses, so a true fever is usually considered a temperature above 38.9C (102F) .
Taking a horse's temperature is a standard part of any physical examination. A high temperature usually triggers concern about infection, and leads to further investigation. A few things need to be considered when taking and interpreting a horse's temperature.
An accurate reading is critical. The thermometer used must be in good working order. New, digital thermometers are cheap and accurate, and usually the best option.- If there is air in the rectum, the horse's temperature may read falsely low. This is most problematic if someone has performed a rectal exam shortly before taking the animal's temperature. This is one reason that the temperature is taken early in an examination.
- There are some horses that normally have a temperature outside the range that is considered "normal" for the majority of other horses. Knowing your individual horse's normal temperature when it's healthy can help interpret temperature changes when your horse is sick.
- Body temperature normally varies throughout the day. This diurnal variation usually follows a regular pattern - usually higher during the day and lower at night. The temperature of an individual horse can vary by as much as 1C (1.8 F) over a 24-hour period. This needs to be considered when interpreting temperature changes in a sick horse.
- A normal body temperature does not rule out infection, especially in young foals. Temperature is just one of many important factors used to identify illness.
- If you are going to take your horse's temperature, make sure you know how to do it safely. Don't get kicked in the process. Make sure you are always in a safe position. Although it may seem counter-intuitive, the closer you stand to a horse, the harder it is for the horse to kick you hard. Don't rely on your horse's normal good temperament, especially if it's sick. Animals that are sick or in pain may turn on even their closest companions.
- Don't let go of the thermometer... ever.
On a final, admittedly picky note, when students tell me a horse "has a temperature", I usually respond "So does a dead horse. Everything has a temperature. Does it have a fever?" Does that make me an anal academic (pardon the pun)?
