Going Green

Thursday, December 13, 2007

Hypothermia in Cattle

When we see cattle grazing lush wheat pastures in the fall and winter months, we typically don’t think about the effects of cold or wet weather on those cattle. They usually have a nice thick coat of hair that protects them from the elements. What we often fail to realize is that certain weather conditions or other factors can mean that luxuriant coat is inadequate to keep the animals from suffering hypothermia.

Hypothermia is defined as the lowering of body core temperature below normal values. A cow typically will have an internal body temperature as measured rectally of approximately 101° F. Mild hypothermia occurs when the body temperature is in the range of 86°-89° F. Moderate hypothermia occurs at 71°-85° and profound hypothermia under 50°. At a rectal temperature below 82° the bovine can no longer return to normal temperature without external heat and warmed fluid therapy.

The environmental temperature at which a cow will begin to experience hypothermia varies with length of hair coat, wind speed, moisture and body condition. When hypothermia occurs, the animal’s internal processes begin to slow. Blood is shunted away from the extremities in an effort to protect vital organs and frostbite of the teats and ear tips will occur. As the body temperature continues to lower, respiration and heart rate slow and blood pressure drops. Eventually the animal will lose consciousness and death will occur.

One of the worst conditions for cattle to endure is temperatures hovering slightly above freezing with a cold rain falling. The rain often soaks through the hair coat to the skin and begins to draw heat from the animal’s body. If this condition is accompanied by strong winds, the chilling effect is increased and the animal may suffer hypothermia in a very short period of time. Any time the forecast calls for wet, rainy, windy conditions, steps should be taken to provide at least some form of break from the wind. This can be accomplished by lining round bales of hay or attaching plywood to portable fence panels if better shelter is unavailable.

Light-weight cattle shipped from warmer areas often have a shorter hair coat than native or northern cattle. They also will typically have little if any fat that would act as an insulating factor in inclement weather. These light-weight stockers also may be undergoing the stress of disease exposure, long shipping distances, recent weaning, or other factors that challenge the body and require energy to overcome. When extreme cold stress is added to those factors, they become at high-risk for hypothermia.

Newborn calves also are at high risk for hypothermia. They are born with a wet hair coat which is often fairly short. If they are born in cold or wet conditions, care should be taken to provide shelter for them. Many calves born under extreme conditions lose body heat quickly and never gain enough strength to stand and nurse. If cows are calving during extreme conditions, they should be monitored closely or moved to shelter prior to calving. Preparation should be made to have warming blankets, heat lamps and clean, dry bedding in a sheltered place available to warm hypothermic calves should they be born in such conditions.

Prolonged wet, cold conditions will take a toll on all types of cattle. The body must fight to maintain sufficient core temperature to sustain itself during such conditions. It is critical that adequate feed and drinkable water be supplied. Typically feed intake will be elevated prior to onset of a storm and then somewhat depressed during the inclement weather. This suppressed appetite means that the quality of available feed must be high in order for the animal to get the greatest amount of nutrition possible during such conditions.

To minimize death loss in cattle due to hypothermia, shelter from rain and wind, adequate high-quality feed, and sufficient drinkable water are critical. If cattle become hypothermic, steps may be necessary to raise their core body temperature through therapy such as warmed fluids and moving the animal to a heated shelter. The best plan is to make preparations prior to such conditions rather than providing emergency treatment afterwards. Always seek the advice of a qualified veterinarian on any questions of animal health.

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