Heat stress in calves

Would you know how to recognise heat stress in calves? We discuss symptoms and prevention methods to keep your calves safe.

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Now that we are (hopefully!) entering into some more pleasant summer weather, it is worth remembering that both cows and calves can sometimes struggle in the warm weather, just as we do. If you are sweating, your animals are likely to be sweating too!

For calves, their upper critical temperature (the temperature above which the calves’ internal body temperature begins to rise and they become ‘heat stressed’) is 25 C. Once this ambient temperature is reached then calves must use energy to try and keep cool, typically through the following methods:

• Breathing quicker
• Drinking more milk and eating less solid feed
• Drinking more water
• Spending more time standing up rather than laying down

The energy required to cool the body down is diverted from other essential functions and, as such, growth and the ability of the immune system to fight infections are typically reduced.

There are several things that we can do to help reduce the chances of heat stress and minimise the negative effects on calf growth rates and the immune system. These include:

• Allowing access to clean, fresh water at all times.
• Keeping water out of the sunlight and changing it often. Locating water troughs/buckets away from bedding is also useful to prevent wet bedding which can then heat up.
• Monitoring the temperature inside calf accommodation. This should be done at calf level as the temperature may be higher here than higher up within the shed. Increasing the airflow in the shed can also be considered so long as draughts are not created at calf level as this can then lead to chilling.
• Checking on the calves regularly for signs of heat stress (sweating, panting, excessive drinking). You can also monitor the rectal temperature of calves with a temperature (in an otherwise healthy calf) over 39.4 C being indicative of heat-stress.
• Allowing access to increased volumes of milk or concentration of milk solids as a source of extra energy.
• Providing shade for calves will help to keep calves cool and providing good fly control can help reduce the spread of fly-borne diseases.
• Keeping water and milk feeding equipment clean and disinfected – warm weather promotes bacterial growth on this equipment.

It is important to remember that in sheds with poor airflow, high humidity and high stocking density, you can still see signs of heat stress in animals even when the weather is not that warm! This can especially be true in sheds with clear ‘roof light’ panels in the roof, as although they reduce the need for electrical lighting, they can vastly increase the temperature within a shed. These type of roof panels should only ever be fitted to the north-facing aspects of building to minimise this issue. If you have any further questions or queries about heat stress in calves, please contact us at the practice.

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