A freshly shorn sheep, especially if in light condition, may experience a threefold increase in heat loss and therefore prone to hypothermia.
Shorn sheep are at greatest risk of cold stress in the first three days (or nights) after shearing, and remain at risk for up to two weeks, with mortalities seen in some mobs up to four weeks after shearing.
Although there is little wool growth, acclimatisation and considerable skin thickening occur after shearing.
It is therefore essential to closely monitor predicted weather conditions before putting shorn sheep into a paddock after shearing.
The impact of cold weather, particularly when combined with wet and windy conditions, can be severe for sheep.
The impact of the cold weather will depend on its duration, rainfall, wind speed, and temperature.
The type of weather most likely to cause catastrophic sheep losses due to hypothermia is usually associated with the passage of a strong cold front or a rain-bearing depression.
Sheep grazier alerts are issued when a combination of rain, wind, and low temperatures reaches a critical level.
If a sheep grazier alert has been received at the end of shearing, shed as many sheep as possible and provide hay for the duration.
Once the bad weather has passed, move the sheep to a paddock with adequate shelter and continue to provide supplementary feed.
In areas prone to winter storms, a ‘cover comb’ or ‘snow comb’ can be used, which leaves 0.5cm of wool to help protect against hypothermia.
Once freshly shorn sheep get cold, they may become extremely difficult to move, so always put shorn sheep into a protected paddock with plenty of shelter from the cold and wind.
Off-shears paddocks should be small and well protected from cold winds by relatively impermeable shelter belts.
Extra feed should be provided to the mob for up to four weeks following shearing to meet their increased energy requirements.
Shearing a month before lambing encourages ewes to seek shelter and hence protection for their lambs.
However, pre-lambing shearing must only be considered if ewes are in good condition and have free access to good feed and shelter.
Heavily pregnant ewes should not be subject to the handling and feed deprivation that shearing involves.
For further information, contact your local veterinarian, Agriculture Victoria veterinary or animal health officer, or in NSW, your Local Land Services.
Dr Jeff Cave is an Agriculture Victoria senior veterinary officer.
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