At the height of summer, heat stress in livestock can become a major issue for production levels and animal welfare.
The ideal temperature range for cattle is between 5° and 25°C, and for adult pigs just 18° to 20°C.
High-producing livestock, such as dairy cows, are the most sensitive to heat stress.
Poultry have been known to perish due to heat stress on hot days.
As temperatures rise, livestock have to divert energy away from production to cool themselves. This is done via heat loss through their skin surface and respiratory tract.
Feed intake is also reduced and a decrease in milk production may be observed.
Humidity also plays a significant role in heat stress. For any given temperature, the degree of heat stress increases as the relative humidity increases.
Heat-stressed livestock will seek out shade, drink more, eat less, stand rather than lay, pant, produce less milk and be less fertile.
Deaths can occur due to heat stroke on hot days.
On hot days, livestock should be given access to shade and good quality, cool drinking water.
The yarding and movement of livestock should be avoided during the hottest part of the day.
High quality feed should be given during the evening when it is cooler and the livestock are likely to have better intakes.
Your fire plan may need to be enacted on such days.
Heat stress can have significant impacts on production and animal welfare.
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.
■For further information, contact your local veterinarian or Agriculture Victoria veterinary or animal health officer, or in NSW your Local Land Services.
—Dr Jeff Cave
district veterinary officer