Young calves are very susceptible to low temperatures. They are on highly digestible feed and are not yet ruminating so less heat is generated by digestion.
During their first week of life and when temperatures plummet to less than 15°C, they’ll start using energy from feed to keep warm. High risk calves – those with a difficult birth and twins, will feel cold at higher temperatures.
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 and Its Impact
- Energy is diverted from growth to maintaining body temperature
- Growth rates will fall and calves will become more susceptible to disease
How to Prevent Cold Stress
Have a plan for when cold stress is likely to happen, that’s when the ambient temperature drops below 15°C, or at a higher temperature for high-risk calves.
1. CALF FEEDING
- Make sure every calf receives adequate quality colostrum
- 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
Table 1: Increase in energy supplied by increasing calf milk powder oil content or feed rate
- Increase the level of milk solids by 100g per day for every 10°C temperature drop below 20°C to maintain growth rates. See figure 1.
Fig 1: Additional calf milk replacer required to maintain growth rates in cold weather, for a calf aged 0 to three weeks or older than three weeks of age:
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
- Ensure bedding is kept clean and dry and provide plenty of deep straw bedding; it provides them 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 jackets
- Provide an external heat source close to calves
Finally, calves born on very cold days take longer to stand and suckle so they may not receive enough colostrum to ensure adequate transfer of immunity. Make sure they each receive a minimum three litres or six pints within three hours of birth – use a teated bottle or stomach tube.