10 Top tips for managing calves in hot weather

How 1

Baby calves will suffer heat stress when temperatures exceed 26 °C, and bacterial challenges will also rise.

Key focus areas: Shade, ventilation, hygiene, feeds and flies.

  1. Shade and Ventilation. Calves kept in single hutches need outdoor shade, and increased airflow. E.g. Calf Gardens for hutches and a veranda for groups work very well. 
How 2


  1. Jack up the back of the hutch on bricks to encourage airflow. Put a thermometer inside the hutch to monitor temperature. The use of fans in a calf shed can also help. Colostrum storage and handling Colostrum and milk are the perfect breeding grounds for bacteria in hot weather. Even at 20 °C the population of coliforms can double every 20 minutes, so rapid cooling of excess colostrum and refrigeration or freezing are recommended. 

  2. Use milk from the cool bulk tank or create a simple cooling system for milk and colostrum. Take some empty colostrum bags and fill with water. Freeze down, then when required, plunge into the barrel of milk to be cooled. When totally defrosted the 5L of ice can be refrozen and used again. The ratio is 5L of ice to 20L of milk to cool rapidly.
How 3


  1. Avoid using high cell count or mastitic milk for ad-lib feeding as it will spoil quickly.

  2. Use a preservative for milk or colostrum e.g. Preserver milk preservative from Pyon. This will help to reduce spoilage bacteria developing for up to 24 hours. Cheap and effective, 1.5p/L in use.  

  3. Store milk in the shade, and never mix old milk with fresh.

  4. Hygiene: wash all vessels containing milk at least once a day using a detergent steriliser to remove fat and protein build up. Algae will grow in warm water. Scrub buckets daily and refresh with cold water. 

  5. Feeds: Calf starter pellets and meal will go rancid and mites can develop quickly in hot weather, so keep it fresh and offer it ‘little and often’ to encourage intakes. Calves prefer a shallow bucket or trough to lick clean.
How 4
  1. Water: 5L of cold water will be consumed for every 1kg of dry feed consumed. Cold water will help to bring down body temperature on a hot day. As air temperature rises from 20° C to 30° C an extra litre of water is needed to cool the calf.

  2. Flies spread disease and irritate the calf. Pour on fly control will keep nuisance flies at bay, and kills lice at the same time! Using one with a graduated dose rate saves cost e.g. Flypor or Swish. 
How 5

Paint a board with insecticide e.g. “Twenty One” is recommended for flies in housing. Hang up as a target to attract flies in the calf shed - very effective.

Fly control available through Agri Retail outlets. 

Gill Dickson (Youngstock Advisor)

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