Managing heat load is a very real problem for dairy cows over the warmer months and can have major implications for both productivity and animal health.

High temperatures and humidity make it difficult for cows to cool themselves. As heat stress builds, they stop producing milk and focus on handling the heat.

During summer, cows rely on cool conditions overnight to reduce their heat load. When hot days and warm nights combine with high humidity, heat stress builds up. When these conditions persist, the heat load can have a major impact on productivity and profitability.

For example, in 2017 there was a persistent heat wave across Victoria and Tasmania with above-average temperatures both day and night in the second half of November. University of Melbourne research estimates that a dairy farm with average milk production of 5,860 litres a day would have lost around $3000 due to this heat wave.

To limit the impact of heat stress on milk production it is more effective to prevent or reduce heat stress than to manage the consequences once cows have succumbed.

Cool Cows

To help Australian dairy farmers prepare for heat events, Dairy Australia has combined with Katestone to provide free heat alerts. The Cool Cows Dairy Forecast Service provides farmers with customisable alerts when hot and humid weather is on its way. The alerts are based on Bureau of Meteorology data and tailored to your specific farm location, not just the nearest town. Farmers can receive alerts by email or SMS.

The site also has detailed seven-day forecasts for towns in dairy regions across Australia (Figure 1).

Figure 1. Cool Cows provides detailed seven-day forecasts for towns in dairy regions. Source: Katestone.

Farmers can use the predicted Temperature Humidity Index (THI) to manage thermal heat load in their cows (Figure 2). The THI is calculated from the air temperature and dew point temperature.

 

Figure 2. Cool Cows gives provides registered users with free heat alerts and the forecast temperature humidity index (THI) for their property. Source: Katestone.

Customisation allows dairy farmers to select the most appropriate THI thresholds to adapt the alerts to their particular environment. For instance, Queensland farmers may choose to set their alert thresholds higher because their cows are more adapted to heat and they are more likely to have cooling infrastructure (such as shelter, sprinklers and fans) in place.

Managing the heat

The biggest stresses occur when there are unexpected heat events in locations where the cows are less adapted to heat. For instance, Tasmanian farmers are less likely to have infrastructure in place to deal with high heat and their cattle breeds are less tolerant to hot conditions than those favoured in northern Australia.

There are a range of both short and long-term strategies that dairy farmers can implement to help their cows beat the heat.

The first priority is to provide shade and good access to water after milking – for instance in the yards. Keep water sources sheltered as cows will drink two or three times more when the water is cool. Changing the milking time (before 10am and after 5pm) and taking feed to the cows to limit their need to walk are also good strategies that are easy to implement.

When heat events become more common it is worth spending money on building infrastructure designed to reduce heat. Dairy farmers in Northern Victoria typically have shade infrastructure around the milking shed with a sprinkler system to allow them to cool the cows at milking (Figure 3). Fans can be added to increase air flow for more effective cooling.

Figure 3. Shade infrastructure with a sprinkler system around the milking shed provides welcome relief from heat. Source: Dairy Australia.

Heat load is cumulative. Dairy Australia’s heat alerts can help farmers to better prepare for and manage heat events to limit the impact on their cows’ health and productivity.

Register for the Dairy Forecast Service at the Dairy Australia Cool Cows website, where you will also find more information about the impact of heat load and practical management options.

Contacts

Alison Kelly, 03 9694 3717, 0400 499 110, alison.kelly@dairyaustralia.com.au

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