Falling temperatures mean that calves will have less energy available for growth and for immune function. To maintain targeted performance, they will require additional feed and management.
Dairy calves can grow at an average 0.8kg per day in their first few weeks under normal conditions, if fed sufficient levels of milk (900g of milk solids), alongside dry feed and water; that’s when the environmental temperatures range between 15°C and 25°C, what’s termed the “thermoneutral zone” (see image).
During their first three weeks of life, and when temperatures plummet to less than 15°C, calves start using energy from feed to keep warm. High risk calves, those with a difficult birth and twins, are more vulnerable and will feel cold at higher temperatures. In fact, daily energy requirements increase by up to 30% once the temperature drops below freezing.
By their fourth week, they’ll be more robust and won’t feel the cold until about 0°C. However, high moisture levels and draughts will dramatically increase their susceptibility to cold stress. Draughts of just 5mph will make calves feel 8-10°C colder.
Cold stress results in energy being diverted from growth to maintaining body temperature. Consequently, growth rates will fall and the calf will become more susceptible to disease since less energy is also available for immune function, meaning that calves are more susceptible to respiratory infections and scours.
Adopting the following three-point plan will help calves to cope in periods of very cold weather, avoid stress, and maintain daily liveweight gain.
• Make sure every calf receives adequate quality colostrum, by stomach tube or bottle, within the first few hours of life
• Step up energy intake; this can be done by increasing the amount of milk offered per day, (see table 1). Increasing the oil content of the milk replacer from 16%
to 20% has a negligible effect on daily energy intake.
• Increase the level of milk solids by 100g per day for every 10oC temperature drop below 20oC to maintain growth rates (see Fig 1)
2. General housing considerations
• Reduce cold drafts whilst maintaining adequate ventilation. Provide effective barriers to drafts at calf level and places for the calves to shelter; plastic and timber are better insulating materials than concrete and steel
• Put in place a system to drain moisture
• Provide plenty of deep straw bedding; it provides calves with a great deal of insulation and reduces body heat loss
• Keep bedding dry and clean – much of the insulation value of bedding is lost when it is wet
3. Specific intervention measures
• Provide calf coats
• Provide an external heat source close to calves
Cold weather is yet another challenge that you can help your calves overcome if you feed for growth and make sure they are properly housed. Well grown heifers will remain on target to join the milking herd at two years of age and are more likely to lead long and healthy lives.