Calves and heat stress

By on May 21, 2024
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Calves and heat stress

It’s only May, but it’s time to prepare for heat stress.   There are several key points to address.

  • Start with the dry cow.  Research in Florida has shown that calves born from “cooled” cows were more efficient in absorbing colostrum IgG, had higher birth weights, greater survival to 1st lactation and produced more milk during their first lactation.
  • Calves are more successful in dealing with heat stress than cows. This is because, proportionally, they have a great surface area / unit of body weight.
  • Different housing systems are more effective in dealing with heat than others.

Managing heat stress in different housing systems.

Calf hutches –  Although they are views as the “gold standard” by many they are not as effective in accommodating heat stress.    Propping up the back of the hutch provides minimal access to fresh air.   Placing shade cloths over hutches is most effective but not practical in larger calf systems, especially where excessive wind is found.   Systems which “wrap” the hutch with reflective material are also effective but have not been widely used  (  Regardless of the strategy for dealing with shade, the hutch systems do not deal with ventilation effectively.    Wisconsin workers (2024)  found that actively ventilating hutches improved the climate, but did not influence calf outcomes as calves spent more time outside the hutch.

Calf “barn”  facility management

  • Ventilation – Insist on mechanical ventilation as even with open side walls, there is not always ambient wind. Consult the Dairyland Initiative for the most up-to-date recommendations.
  • Insulation in the roof reduces heat exposure.
  • Calf starter grain. Most calf starters will have at least 18% CP.   The most key factor is to formulate starters which are palatable and encourage intake.   Coarsely ground or whole corn is preferable.   Keep it fresh, which means feeding more frequently in hot weather and removing spoiled feed.   Position buckets or bunks for starters away from water sources to keep water clean and feed dry.
  • Water is key to success and should be provided from day one. Feeding water and milk in the same bucket is problematic.   Hand clean water systems daily.

Managing the autofeeder system.   

  • Another excellent feature of the autofeeder system is that cleaning can be partially automated. Depending on the age of the system.   Mixer/heat exchanger cleanings are scheduled to clean and sanitize the internal workings of the feeder four times/ day.   Newer systems will do this to include the milk lines and internal surface of the   
  • Make sure settings are correct for unique detergents formulated to operate under lower temperatures than those used in milk systems. 
  • Inspect milk lines (from the mixer to the nipple) and replace them more frequently or when residue is evident.
  • Minimize length of the milk lines to avoid “low” spots in the lines where milk can collect between feedings. Preferably, the line should slope down from the teat to the autofeeder. 
  • Clean and inspect nipples daily. Remove them, hand clean and sanitize them, allow them to dry and replace them with one from the day before.  Discard nipples that show cracking  and wear.
  • Stocking levels. Low stocking of pens does have a downside in that there is not as much milk flowing through the lines from the feeder to the teat and bacteria counts tend to be higher.  For smaller herds with less than 10 calves/ pen, pay closer attention to keeping the system clean.
  • Build facilities to provide at least 40 sq. ft. or 3.7 sq. meters per calf in resting area. 
  • The 40 FIT feed plan allows calves to access feed ad libitum. We commonly limit each meal to ~ 2L.   This allows calves to shift their feeding times to cooler times of the day.  Surprisingly heat stress increases nutrient requirements, just when calves are not as interested in eating, particularly for bottle fed calves and the afternoon feeding.
  • Data management. An excellent feature of autofeeders is that the manager can monitor milk consumption more closely and identify calves that need attention at an earlier stage of disease.

Group housing and autofeeder summary.

Although calf hutches have some very desirable attributes they are not well suited to addressing heat stress challenges with calves.  Ventilation is inadequate and methods to limit heat stress are not practical in many farms.  Autofeeder systems can provide more labor efficient and effective alternative to hutches which enable more “natural feeding behavior,” improved sanitation and a  more desirable environment for calf feeding personnel as well as calves.    Under today’s market conditions, calf management must not be viewed as a daily cost but must consider the long-term impact on health and productivity of the animal.    


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