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Top tips for minimising risk of cold stress in calves
Young calves can rapidly lose heat and this puts them at high risk of cold stress in their first month.
A calf’s thermoneutral zone from birth to four weeks of age is between 10°C and 25°C, illustrated in Chart 1, adapted from Davis and Drackley (1998)

When temperatures go below the calf’s lower critical limit, the animal must draw on energy that it would otherwise have used for growth and to support its immune system.
Failure to generate enough heat can also result in secondary complications such as digestive and respiratory disorders, scouring and pneumonia, which all affect future performance and increase mortality (Young, 1983).
So what can rearers do to ensure calves instead direct energy to maintaining health and performance?

Feed colostrum and transition milk for longer
Colostrum and transition milk not only provide passive immunity to the baby calf in the form of antibodies but also lactose, amino acids, and triglycerides which are excellent energy sources.
For that reason, colostrum and transition milk therefore also play an important role in thermogenesis.
Extended feeding is strongly recommended to support the needs of the newborn calf.
Ensure calves have a deep dry bed of straw
Calves should almost be hidden in their bed of straw.
Research from the Wisconsin-Madison University recommends a nesting score of 3 (Lago et al., 2006) with the calf’s legs completely covered by the bedding.
Straw provides comfort and is a great insulator from the cold ground, and a barrier to moisture such as urine and milk.
Keep beds dry by replenishing straw regularly. A quick test is to kneel – if knees become wet more bedding is needed.
Use calf jackets or introduce a heat lamp
Jackets are a great way to keep calves warm in the colder winter months.
These should be made from a breathable material to prevent sweating on warmer days or as the calf gets older.
Before coats are transferred to another calf, it is vitally important that they are thoroughly washed at a temperature of 60°C or higher temperature to kill bugs such as cryptosporidia.
Providing baby calves with heat lamps can also be beneficial, especially in the early hours of life.
Prevent draughts
It is important that calves aren’t exposed to low level draughts as these can cause a chill.
Research (Diesch et al., 2004) showed that calves born during windy and wet weather, and when temperatures were less than 10°C, had lower rectal temperatures immediately after birth and took longer to stand when compared to calves born in dry weather and when temperatures were greater than 10°C.
Using a windbreaker or adding some temporary straw bales can provide good shelter during cold, stormy weather.
Don’t tweak feed plans to suit the weather
Consistency is key in calf rearing.
It is not advisable to increase or decrease milk volume or concentration according to weather conditions. It is best to stick to the usual feed plan while making the calf’s environment warmer.
This will of course differ according to country and climate – if winters are always very cold and well below the baby calf’s critical temperature, feeding a greater milk volume may be a good option.
As calves get older, they can withstand lower temperatures because their hair is thicker and longer, skin is thicker, the rumen is developing and there are stores of subcutaneous fat.
But for a calf in its first month of life, it is essential to create a warm environment and to provide the correct nutrition for a healthy and productive start.
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