Protocol

Thermo-Neutral Zone

The thermo-neutral zone of a calf is the range of temperature in which the animal uses no additional energy to maintain its body temperature.

In new born calves and up to four weeks of age this is typically between 10°C and 15°C. Within this, the calf will generally maintain its body temperature and requires no additional energy to keep warm. Outside these temperatures i.e. if it is too cold calves must burn energy just to maintain core body temperature.

A calf requires 2% more energy for every 1°C below the thermo-neutral zone, therefore at freezing point (0°C) a calf requires 20% more milk/feed just for maintenance.

Dairy breed calves do not have enough body fat to maintain their own body temperature in cold weather. Feed is often limited by number of feeds per day and the amount given per feed. Keeping the calf warm therefore is the most cost effective way of maximising the feed given.

Calf Jacket Protocol

Calf Jackets keep calves warm, dry and healthy, in the winter when temperatures fall below 10°C.
More energy is used to keep warm and less energy on development and growth. Remember, calf jackets do not replace good calf husbandry.

  1. Using a thermometer, monitor and record the min-max temperature in the calf shed and reset every day during the autumn and winter months.
  2. Decide on a set trigger temperature for your system, e.g. 10°C.
  3. Set protocol at which the calves will start to experience cold stress, e.g. 3 consecutive nights with temperature below 10°C.
  4. Young calves (less than 3 weeks of age) are most susceptible to cold stress, therefore assess them first.
  5. Only put jackets on dry calves.
  6. Place clean jackets on every calf below 1 week of age and on entry to calf shed.
  7. Make sure the jacket fits the calf so that it covers the calf’s body from neck to tail.
  8. Adjust the straps according to growth.

Removing Calf Jackets

  1. Removal of jackets will be entirely dependent on weather and appetite of each calf.
  2. Be aware not to remove jackets too early.
  3. Set protocol for removing jackets based on age of calf and ambient temperature:
    • 1 week old > 15°C
    • 2 weeks > 5°C
    • more than 3 weeks > 2°C
  4. Refer to recent night-time minimum temperatures.
  5. Remember to consider individual calf condition; feed intake, health, growth rate.
  6. Remove calf jacket in morning not afternoon.

Tips

  1. To preserve body heat ensure calves have enough dry bedding to nest.
  2. Monitor jackets for cleanliness and replace soiled or wet jackets with a clean, dry one.
  3. Remove dirt from jackets with a hose or light power-wash, if necessary pre-soak.
  4. Jackets must be washed at minimum 30°C with detergent and thoroughly dried between each use.