Heat stress in livestock can become a major issue both for production levels and animal welfare but there are precautions that can be taken, says Agriculture Victoria district veterinary officer Dr Jeff Cave.
The ideal temperature range for cattle is between 5 and 25 degrees, and for adult pigs just 18 to 20, he said.
High producing livestock, such as dairy cows, are the animals most sensitive to heat stress and poultry have been known to perish due to heat stress on very hot days.
"As temperatures rise, animals use their energy to cool themselves - this results in reduced production or weight gain," he said.
"Feed intake is also reduced further increasing these impacts."
He said high humidity could also play a significant role in heat stress.
For any given temperature, the degree of heat stress increases as the relative humidity increases.
Dr Cave recommended checking livestock daily and looking for any signs of stress during hot weather.
"Heat stress can significantly impact the production and animal welfare of your stock," he said.
"Heat stressed livestock will seek out shade, drink more, eat less, stand rather than laying down, pant, may produce less milk and can be less fertile.
"On hot days, give livestock unlimited access to shade or shelter and good quality, cool drinking water. Make sure you are ready to implement your fire plan."
He advised against moving animals during the hottest part of the day and urged producers to avoid it on extreme days.
High quality feed should be given during the evening when it is cooler, as livestock are more likely to have consume it.
If you are not living at a property, arrange for a neighbour to check on animals in your absence, he said.
"All producers have an obligation to ensure livestock in their care are free from pain, suffering or distress," he said.
"Failure to provide livestock with adequate food, water or shelter may be an offence under the Prevention of Cruelty to Animals Act 1986.
"By making some minor management changes and taking a little extra care of your livestock in extreme hot weather, the effects of heat stress can be substantially reduced delivering better welfare and production outcomes."
For further information please contact your local veterinarian or Agriculture Victoria veterinary or animal health officer, or in NSW your Local Land Services.