The stalled horse, shelter, and anemia...
CHOOSING SHELTER FOR THE HORSE
Last week we visited about the management of our horses in this intense summer heat. The horse that stays outside will find the cool areas of the pastures. They find where the air flow is greatest and use it to stay cool in the summer, and where to avoid the breeze in the winter.
The horse is equipped with a cooling mechanism based on evaporation of moisture. The sweat caries heat and moisture to the surface of the skin. Evaporation of the sweat releases heat to the environment. To a lesser extent rapid breathing will help remove heat from the heat exchanger known as the lungs. The blood flow within the lungs is within vessels that are only one or two cells thick. The incoming air will be a little cooler than the horse’s body temperature. It will lower the temperature of the blood a little (or a lot if the air it is breathing is cool). As the horse exhales, the air will carry out heat. This is not as efficient as sweating because of the surface area difference. The respiration rate gives us an indication of the body temperature in the resting horse. An increased respiration indicates an elevated body temperature. These cooling processes are kept in mind when planning facilities, and caring for horses during the heat.
Should we provide shade for the horse in the pasture? I think we all feel better knowing the horse has access to shade, and will invest money to see they have it. We may, however, have second thoughts when we see horses standing in the sun right next to the shelter! I have often wondered in both winter and summer if the shelters are to make the passing motorist feel better about the conditions under which the horses are kept ( tongue in cheek). The horses will use shelter to protect against the wind of winter. In the summer, its shade serves multiple functions. It protects the horse from the sun. Because it is out of the sun it will be a cooler place to hang out. If there is air movement, it will be cooler and breathing it will cool the horse more rapidly. The cooler air will make the sweat soaked hair feel cooler. And a big advantage of shelter is that the horse flies are not as bad under shade.
No article would be complete without a plug for good health care. The blood serves a very important role in maintaining the temperature of the horse. In addition to the lungs as we discussed above, it also provides a heat exchanger for the skin. The heat is released from the skin and the cooled blood is returned to the pipeline . If the blood is “thin” it is low in red blood cells (RBC) and hemoglobin, the oxygen carriers. So in the anemic horse, a great deal more volume of blood is needed to provide enough blood cells to transport oxygen from the lungs. To pump more blood requires the heart to work harder. This extra exertion alone increases the work load, but the blood low in RBCs is not as dense. The denser the blood, the more heat it will absorb, making the transport of heat from inside the body to the skin more efficient. Anemic blood means a hotter horse.
Anemia can be due to a number of diseases and conditions, but the most common is a heavy parasite load. Most common are the internal parasites (worms), but a heavy infestation of ticks and lice can also make the horse anemic. Disease of the liver, kidneys, and bone marrow will cause anemia. The first step is to determine if Dobbin has a low blood count. This can be done with a quick blood test. Once anemia is diagnosed, we can start looking for and correcting the cause. It is unfortunate that the less healthy horse, that may also be running a fever, has the most difficulty staying cool.
Many of the above topics also apply to the stalled horses, so we are using this article as the transition between the stalled and the outside horse. More on that next week.
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