Heat tolerance and extreme weather stress is under the microscope, as research seeks to identify genetic and production differences in dairy herds in Australia.
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Farmers are being warned to provide shelter from storms and severe weather, including the hot sun, for their livestock.
“Infrastructure that will enable the livestock to get behind the storm, or away from the rain and wind, would be a suitable form of shelter,” Agriculture Victoria veterinarian Dianne Phillips said.
Dr Phillips said some farmers had reported livestock losses in the severe storms and rain events of the past few months.
“Vulnerable groups of livestock have been experiencing the severe weather events,” she said.
“Severe weather can include high winds, concentrated rainfall, hail and sudden temperature changes.”
Dr Phillips said farmers should ensure their livestock are up to date with routine stock health management, including drenching and vaccinations and to monitor for diseases.
“Good health helps animals to better adapt to changing weather conditions,” she said.
AgVic dairy extension officer at Tatura in northern Victoria, Richard Smith, said dairy farmers should have in place heat stress management programs for their herds.
“Heat stress has been shown to decrease milk yield up to 25 per cent, reduce feed intake up to 20 per cent, and negatively impact fertility, artificial insemination and natural conception rates, and in-calf rates,” Mr Smith said.
“Modelling has shown when shade is provided, there are 53 per cent fewer moderate and 86 per cent few severe heat stress events.
“Shade, sprinklers and air movement enables faster milk let-down and more incentive for the herd to walk to the dairy.”
He also recommended installing a shade structure over feedpads.
Ellinbank Research Farm is undertaking research into the effect of extreme weather events on cow production, including heat stress.
DataGene is also undertaking research that identifies genotypes for heat tolerance.
“Since 2018, DataGene has implemented the heat tolerance value,” DataGene chief executive officer Matt Shaffer said.
“DairyBio has done some additional work, and that information will be available to farmers soon.
“Australia is the first country to introduce a heat tolerance ABV, and there’s quite a few farmers across Australia who use it.
“Discussion about its effectiveness is increasing in Australia’s northern states and overseas.”
Cooler cows
Dairy Australia has produced resources to help identify when cows could be in distress and how to manage that.
Cows start to actively manage their core body temperature when it is below 5°C and above 25°C.
In hot weather, cows use methods to effectively disperse heat including standing in water, shade or a breeze. They also pant and reduce their feed intake.
As air humidity and temperature increase, the effectiveness of evaporation strategies used by cows rapidly declines.
Heat affects reproduction, milk production and can lead to severe heat stress, which can lead to death.
Trees planted in paddocks or laneways can reduce the radiant heat load by 50 per cent or more. Orienting the long axis of paddocks north-south will help maximise shade throughout the day.
The dairy yard is another place where heat rises — cows are standing close together and their body temperature can rise quickly.
Use sprinklers, hoses or the flood wash to pre-wet your dairy holding yard for an hour before the cows arrive for afternoon milking.
Finish morning milking before 9am and delay afternoon milking to after 5pm on hot days.
Consider a shade structure and fans as the next upgrade for the dairy holding yard. At the same time, ensure food and water are in adequate supply nearby.
In hot weather, cows’ daily water consumption doubles to 200 litres and more. Standing in a hot environment and eating grain increases their need for water.
Water makes up 85 per cent of the milk cows produce.
When nights are warm, this reduces the amount of heat a cow can dissipate overnight, and will mean she has a higher temperature the following day.
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