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The frequency of exceptionally hot years is expected to continue across Australia in years to come, which means that consecutive days of extreme temperatures (heat waves) will not be uncommon.
Under normal conditions, farm animals maintain their body temperature at a relatively constant level by employing strategies that balance heat production with heat loss (for example, shivering will produce heat whereas panting will help the animal lose heat). This exchange is best achieved in the so-called thermoneutral zone – a temperature range in which the rate of heat production and heat loss is in equilibrium. Different animals have different thermoneutral zones (approximate figures):
Beef cattle (British breeds) 15 – 25°C
Beef cattle (tropical breeds) 16 – 27°C
Chickens & hens 10 – 20°C
Dairy cattle 5 – 20°C
Goats 10 – 20°C
Pigs 16 – 25°C
Sheep 21 – 31°C
Turkeys 10 – 24°C
During extremely high temperatures, an animal will struggle to lose excess body heat through evaporation. The situation is exacerbated if humidity is high or there is no breeze. Tell-tale signs of heat stress will appear: panting, increased respiration rate, increased drinking, loss of appetite and lethargy. Certain animals are more vulnerable to heat stress, including young, sick, heavily pregnant, dark coated, and heavy animals.
Heat stress can be prevented by providing animals with plenty of shade and fresh, cool water. Animals housed indoors should have well ventilated facilities with plenty of space for all animals to lie down.
Handling (including mustering and husbandry procedures) or transporting animals must be avoided in extreme heat and planned for the cooler parts of the day.
Taking proactive measure to prevent heat stress will help protect the animal’s welfare during periods of extreme heat.