Managing in the heat
Go on alert
Taking action in the heat
If you have been counting cow breaths and keeping a close eye on the weather, you will know when you need to take action and bring all your resources to bear to minimise the impact of an excessive heat load event. Different levels of heat stress warrant different cooling strategies, but they all depend, to some extent, on the preparation that went on in the cool season.
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Consider heat load as a quantity of bricks that the cow must carry.
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Level of heat stress
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Action you might take
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Moderate – THI 75
e.g. 26°C and 65% relative humidity or
30°C and 30% relative humidity
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Provide shade in paddock in afternoon or bring cows up to shade shed prior to afternoon milking and feed fibre or a PMR.
Sprinkle cows at afternoon milking
Ensure adequate buffers and minerals in diet
Ensure free access to cool drinking water
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High – THI 78
e.g. 28°C and 80% relative humidity or
32°C and 30% relative humidity
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Do all of the above, plus:
Change paddock rotation so cows don’t have to walk too far to afternoon milking, and have access to coolest paddocks with best quality pasture overnight
Sprinkle cows at both afternoon and morning milkings
Change afternoon milking time from 3pm to 5pm.
Increase grain/concentrate feeding rate and feed higher quality forage
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Severe – THI 82 plus
e.g. 28.2°C and 90% relative humidity or
36°C and 30% relative humidity
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Do all of the above, plus:
Use fans if insufficient air movement
Make further alterations to feeding management and the diet as appropriate.
Take emergency measures if necessary. e.g. Provide cows with access to a dam
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Ramp your level of actions up or down according to your cows' heat load fluctuations.
