Johanna Marsden BVSc MRCVS, Molecare Farm Vets
As the temperatures really begin to drop and the cold winter months set in, it’s important to review the set up you have for your calves to ensure that they are best equipped to deal with the changes in weather through the coming weeks and months.
Pre-weaned calves are very vulnerable to changes in temperature and will re-direct energy that is needed for growth and maintaining a healthy immune system, into keeping warm. The Lower Critical Temperature (LCT) of a calf is the temperature at which they need extra energy in order to maintain body temperature. For calves less than 3 weeks old their LCT is 10-15⁰C, and in calves over 3 weeks old the LCT is 6-10⁰C. It is important to remember that this will be lowered further if there are draughts at calf height.
In this article we will look at several aspects, including nutrition and housing to ensure that the calf grows well and stays healthy this winter.
By monitoring the temperature of the calf house daily with a maximum and minimum thermometer you will be able to assess what level of cold stress the calves are experiencing so you can adjust the feed accordingly. For every 5⁰C below the LCT, calves should be given an additional 50g/L of milk powder or 0.33L of whole milk. This is based on a calf being fed 6L of milk or milk replacer (at 150g/L, 22% protein and 18% fat) daily. It would also benefit the calf to increase daily feeds from 2 to 3 times a day, to ensure that the feed interval does not exceed 12 hours. As always it is important to have fresh water, starter grain and hay or straw available adlib too.
In cold weather it is tempting to keep the calves warm by closing shutters and covering open areas of the shed. However, a good flow of fresh air is important to have in the shed to stop the build-up of bacteria and reduce cases of pneumonia. It is the air speed at calf height that is the important factor, if it is 0.3m/s or over the calf will get cold. In the calf sheds the walls should be solid till over calf height and have ventilation above.
Straw is expensive this year, however, calves still need enough clean dry bedding to be able to nest. This nesting behaviour enables them to create pockets of warm air within the bedding. One way to know if they have enough bedding is to check that when the calf is lying down you cannot to see their legs. Having good drainage within the shed will also help the bedding to stay dry. Concrete floored pens should have a 1.6% slope across the whole bedded area and a 5% slope at the front where they feed and drink, this should flow into a channel in front of the pens to carry urine and water away.
Jackets and heaters are two additional tools that can be used for calves in the first few weeks of life. If used properly they can be very effective in helping to maintain body temperature in cold weather. Jackets must be changed and cleaned regularly, as once they become wet and dirty, they will then have a detrimental effect on the calf’s health, as a cold and wet jacket will chill them and increase the risk of pneumonia and scours developing. When to remove jackets is another important aspect to consider in this approach. It is best to do so when good weather is forecasted for a few days, with temperatures over 10⁰C and to remove in the morning to give the calf the day to adapt.
Heaters can also be useful for groups of calves, and especially if you have a sick calf. They should be waterproof, have a protective casing and placed so that calves can move away from the heater if needed.
Ensuring the calves are well fed and kept warm this winter will enable them to reach their target daily live weight gain and stay healthy throughout the season. For more information on feeding and housing your calves this winter, please contact your Molecare veterinary surgeon by calling 01392 872934 or emailing [email protected]