Calves expend energy to keep warm. The thermoneutral zone is defined as the temperature at which the animal’s heat loss equals the heat production. The animal does not have to expend extra energy to control its temperature when in the thermoneutral zone. The thermalneutral zone for a new born calf is 50-78 degrees F. This is affected by many variables including wind, moisture, hair coat and bedding. By one month of age, the calf is able to tolerate more cold and the thermoneutral zone expands to 32-78 degrees F.
Normal milk replacer or milk feeding will not be sufficient to meet the extra energy requirements of young calves to keep warm in extreme temperatures. Researchers athave shown that the pounds of milk replacer needed to meet maintenance requirements of a 100 pound calf increases 44 percent when temperatures are 15 degrees F, compared to 50 degrees F. If the temperature drops to 5 degrees F, then the requirement for maintenance increases 55 percent. Energy intake can be increased by adding an additional feeding of milk or milk replacer. If an additional feeding cannot be done, then increasing the milk feeding size, increasing fat content of the milk or the amount of powder mixed in the same amount of water can help the calf fight the cold. Older calves are able to consume more starter to battle the cold.
Extra bedding will help the calf keep warm and dry. When laying down, the calf’s legs should be buried in the straw. Deep bedding will trap warm air in addition to keeping the calf dry. A calf blanket can also be used with deep bedding to give the newborn calf extra protection.
If a young animal is sick, do not withhold milk or milk replacer. The energy from the milk is essential for the calf to fight illness. Electrolytes that provide minerals, energy and protein to the calf should be fed in addition to normal milk feeding for scouring calves. When using electrolytes, do so at least two hours after the calf was given milk. If electrolytes are fed too soon after milk feeding, then the ingredients in the electrolytes can interfere with the clot formation in the abomasum, possibly making the scours worse.