Cold stress on trucked cattle

Introduction

"Death losses in cattle are often greatest when the temperatures are near freezing and either rain or freezing rain blows into a truck," reports Dr. Temple Grandin, a renowned livestock handling expert from Colorado State University.

Hypothermia is a reduction of deep body temperature below normal. This can be caused by prolonged exposure to cold, accompanied by the inability of heat conserving and heat generating systems to keep up with the drop in temperature. If an animal cannot reverse this drop in deep body temperature then it will die.

Many things influence an animal's body temperature

Five factors are

• exercise
• time of day
• digestion
• water consumption an
• environmental temperature.

When the weather turns cold, cattle turn on their heating systems. They try to reduce heat loss through the skin by: curling up when they lie down, having their hair stand more erect to increase the insulation value, a heat exchange between veins and arteries that are close together. If reducing heat loss is not enough to maintain their body temperature, the cattle must start to produce heat.

The temperature where heat production must begin is referred to as the Lower Critical Temperature (LCT). When cattle reach their LCT, they shiver, their metabolism increases and they release energy from fat. The LCT depends on age and size of the animal, environmental temperature, wind and moisture conditions and hair coat.

The LCT of a cattle beast with average hair coat is 0° C (32° F). Having a heavy winter coat will lower an animal's LCT to -7° C (20° F). If the hair coat gets wet, the insulating factor drops and LCT rises to 14° C (57° F). Hair coats matted down by manure or mud are also unable to capture body heat for the animal. Cattle in the back of a moving truck or trailer that is travelling 80 kph on a day the temperature is -1° C (30° F) are experiencing a wind chill factor that makes it feel like -23° C (-10° F).

Temperature fluctuations of more than 20° C (36° F) are very stressful to cattle. The cold stress is amplified when cattle's hair coat becomes wet, robbing them of the insulating qualities of the hair coat. Newly weaned calves in particular need to be protected from both excess dampness and temperature fluctuations. Trucking cattle on dry, cold days lowers the chance of losses due to their hair coat retaining the ability to insulate them against outside temperatures. If you are planning to truck cattle during cold wet weather keep in mind how wet the cattle in back may become in transit.

Cold Weather Precautions Before Transporting

• Supply ample bedding, such as straw, when the temperature is below 10° C (50° F) because it provides good insulation and helps to keep animals warm and dry.
• Remove wet bedding after each trip to prevent it from freezing in the vehicle.
• Overcrowding does not allow animals to reposition themselves and frostbite can occur in individuals.
• Close nose vents in the vehicle.
• Cover bottom ventilation slats in the vehicle to protect cattle from the cold and road spray, but allow for adequate ventilation at all times.

Warning Signs of Cold Stress or Discomfort During Transportation

• Cattle eat available bedding.
• Fluid frozen to the face or nostrils.
• Shivering.

Table 1. Wind Chill Factors

• Kansas State University and Livestock Conservation Institute
• Precautions and warning signs of cold stress and wind chill chart courtesy of Canadian Agri-Food Research Council
• Recommended Code of Practice for the Care and Handling of Farm Animals-Transportation
• Reprinted with permission from Canadian Agri-Food Research Council

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