The effect of temperature on the performance of young calves
With calving well underway, now is a good time to review factors affecting growth rate in the young calf. George Ramsbottom, Teagasc Dairy Specialist focuses on the effect of temperature on the performance of young calves and has practical advice for keeping calves warm here
The following diagram shows the partitioning of the ‘typical feeding rate’ of milk replacer for maintenance and growth at 15°C.
The typical dairy breed calf (birth weight of approximately 35 kg) requires 380 grams of powder per day to maintain itself at 15°C. The remaining 370 grams of milk powder can be used for growth – as a rough rule of thumb, the daily gain supported by the ‘surplus’ powder is half of the surplus quantity. In other words a surplus of 370 grams of milk powder will support an average daily gain of 185 grams. Normally we’d expect the calf to grow at a rate of approximately 500-700 grams per day so get the calves eating meals as quickly as possible to help it to achieve the target daily growth rate.
The lower critical temperature of a calf is the temperature below which it needs to use more energy just to maintain its core body temperature. Young calves become cold stressed at temperatures <10°C – temperatures that are typical in February. For every 5°C drop in temperature below 15°C the young calf (under 3 weeks of age) should receive 50g extra milk powder. If the house is cold and it doesn’t receive extra feed, then growth rates are reduced. Feeding calves at an enhanced level will provide enough energy to support maintenance, growth and the immune system. If nutrition falls below basic requirements the calf’s health system will be compromised.
For every 5°C drop in temperature below 15°C the young calf (under 3 weeks of age) should receive 50g extra milk powder
As the calf grows older it becomes less sensitive to lower temperatures – particularly as the rumen starts to develop – see the following table.
The bedding material of choice to keep young calves warm is straw. A dry bed of straw has a lower critical temperature of 8°C so it is sufficient to maintain the young calf without increasing the energy requirement for maintenance during the typical February; for damp straw this increases to over 10°C; and for calves lying on a dry concrete floor this increases further to 17°C. Concrete is one of the coldest surfaces that a calf can lie on. Therefore it is imperative that calves have a good thick bed of clean dry straw underneath them and that they lie at least 3 inches above the floor. Nesting scores are used to determine how well bedded your calves are in the house. And don’t forget that the young calf will spend 80% of its time lying down so a dry comfortable bed of straw is critically important to its growth.
Other alternatives to help the calves to stay warm include using infra-red lamps in the pens with young calves or the use of jackets.
The Teagasc Dairy Specialists issue an article on a topic of interest to dairy farmers every Monday here on Teagasc Daily. Find more on Teagasc Dairy here