The requirement for additional energy management in a calf house varies according to the calf, the weather, and the quality of the calf house environment. In the first week of life, a calf is likely to spend extra energy staying warm below an air temperature of around 10°C. The actual lower critical temperature for any one calf depends on several factors that affect her energy balance:

What affects a calf's need for a jacket

  • Genetics — a Jersey calf will feel "cold" before, say, a Charolais calf.
  • Birth conditions — normal or prolonged labour; premature or low birth weight; single or twin.
  • Health — vigorous and feeding well, versus apathetic with low feed intake.
  • Nutrition — quality, quantity and timing of colostrum; energy density and dilution of milk powder; adequate intake.
  • Air speed — under 1m/s is good; a draught works against you.
  • Dry bedding — essential; damp bedding pulls energy straight out of the calf.

Putting a jacket on

Jackets must be made of breathable materials. The protocol:

  1. Locate a max/min thermometer in the calf house.
  2. Reset the thermometer every morning through autumn/winter housing.
  3. Decide on a set temperature for your system — for example, 10°C.
  4. Agree a starting protocol with staff — e.g. three consecutive night-time minimums below 10°C.
  5. Dry calves off fully before fitting a jacket.
  6. Place a clean jacket on every calf under one week old, on entry to the calf house or as soon as she's dry after birth.

Taking a jacket off

This depends entirely on the energy dynamics above: the condition and appetite of each calf, and the expected weather. Alternatively, simply keep the jacket on until the calf is 4 weeks old — it can stay on longer with no ill effects, as long as it still fits comfortably.

  • Know the weather forecast — steady or rising temperatures are fine; be cautious removing a jacket ahead of falling temperatures.
  • Agree a temperature protocol with staff, e.g. one week old >10°C OK; two weeks >5°C OK; three weeks+ >2°C OK.
  • Refer back to recent night-time minimum temperatures.
  • Consider each calf's individual condition — feed intake, health, growth rate.
  • Remove jackets in the morning, not the afternoon.
  • Breathable jackets can stay on even with daytime temperatures up to 19–20°C, provided night-time temperatures still fall below 10°C.

Washing and care

  • Remove excess dirt with a hose, light power-wash, or a pre-soak.
  • Wash at 40–50°C with detergent.
  • Line dry, or dry overnight in an aired room. Do not tumble dry.