Biosecurity Tasmania urges owners of sheep to be vigilant
for any signs in their flock of cold stress brought about by the recent icy
conditions. Sheep recently shorn and new lambs could be suffering due
to the weather conditions and all reasonable precautions should
be taken to minimise the effects of cold stress.
Sheep have a natural insulation to extreme weather with
their fleece. In cold, wet and windy conditions, sheep shiver, huddle together
in the mob and seek shelter behind windbreaks to produce and conserve heat.
However, these mechanisms have limits. If weather stress is excessive or
prolonged, the sheep’s capacity to maintain a stable body temperature may be
exceeded and cold stress will result. Hypothermia most commonly occurs in
freshly shorn, light condition sheep during wet and windy conditions at any time
of the year
Hypothermia literally means ‘temperature below normal’,
occurs when too much body heat is lost or too little body heat is produced,
and the result is a drop in body temperature. If weather stress is excessive or
prolonged, a sheep’s capacity to maintain a stable body temperature may be
exceeded, and heat or cold stress will result.
High rainfall and high winds combined with temperatures
below normal will cause mortalities in young animals, especially newly shorn
sheep without shelter. The impact of the cold weather will depend on its
duration, rainfall, wind speed and temperature—the ‘wind chill’ factor can
double heat loss.
Sheep suffering from hypothermia often die as a result of
their own behaviour and their attempts to cope. Sheep move in the direction of
the wind until they are stopped by a barrier such as a fence, gully or creek.
At this point they may pile on top of each other leading to suffocation or
drowning. Sheep may be reluctant or unable to move when wet and cold.
Initially sheep will try to maintain their body temperature
- shallow breathing in order
to reduce the rate of respiration (that is, rapid respiration or panting
causes heat loss)
- seeking shelter
- huddling together
If dealing with a small flock, consider applying garbage
bags as coats for the sheep. Trials have shown that properly fitted plastic
bags can decrease the loss of body heat even in severely hypothermic sheep.
More information on caring for your sheep during cold
weather can be found on the Biosecurity Tasmania website.