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Heat stress: a HOT topic

Coming into summer it is important to recognise the impact that heat stress has on your dairy herd. Dairy cattle, being a European animal, are not made for the Waikato heat and humidity and have been proven to show signs of heat stress at temperatures as low as 23 degrees, which is exceeded almost every day through summer.

Heat stress can lead to a drop in milk production, irritability, early loss of pregnancy, and in extreme cases death. Signs to look out for in your herd are a production drop, panting, shade seeking, and clustering of cows (to try and get in other cows’ shadows). A good tool to determine the risk of heat stress is to use the ‘Temperature Humidity Index’ pictured below, which gives a risk based on the relative humidity and temperature.

There are several ways you can help reduce the impact of heat stress including:

  • Installing sprinklers in the milking yard

  • Ensuring the milking yard isn’t stocked too densely

  • Splitting the herd so that limited time is spent at the cowshed

  • Moving milking to early morning or late afternoon

  • Ideally having multiple troughs and shade in each paddock, as well as a trough in the race if necessary


However, if it is a 30 degree day with 80% humidity, there is little you can do to avoid some level of heat stress. Feeding Propath LQ Zinc (available in the shop) is an additional way to combat heat stress in your herd and has the added benefit of improved hoof and udder health.

When you’re thinking it’s way too hot outside, just keep in mind that you are not the one standing in the sun with a black leather jacket on!


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