Summer has arrived, and Elders Senior Livestock Production Specialist Rob Inglis has provided this handy guide to managing heat stress in sheep.
If the long-range forecast is to be believed, a large percentage of Australia’s sheep breeding areas will experience above average temperatures this summer. This could affect reproductive performance, particularly for those joining ewes between November and February.
How long does the heat event have to be to cause an impact on reproduction?
The reproductive performance of the ewe is most affected by heat stress in the week prior to oestrus, during oestrus and then for the ensuing 5 days.
For rams, relatively short periods of high temperatures (1 to 4 days) can have a negative impact.
However, there is significant variation between rams and ewes in their response to heat stress.
What are the impacts of heat stress that will affect reproductive efficiency?
- Decreased appetite.
- Increased metabolic rate and decreased antioxidant production.
- Decreased quality (and often quantity) of sperm production.
- An increase in production of stress hormones.
- A decrease in mating activity. This may ultimately lead to a protracted lambing.
- Detrimental impacts on the ewe’s ovum and eggs, embryo survival, and the placenta.
- Lower birth weights leading to an increase in lamb mortality.
- A decrease in milk production.
This graphic shows some of the impacts of sustained exposure to high temperatures for ewes. Source: The Sheep Reproductive Strategic Partnership – MLA.
Strategies to avoid heat stress
- Graze paddocks without shade before hot conditions develop.
- Clean troughs or place additional water points to supply access to clean, cool water for all animals.
- Maximise shade and water for ewes at joining and in late gestation, and for stock under 1 year old. These animals are particularly vulnerable to heat stress.
- Administer antioxidant supplements, for example, Multimin Chrome, Beachport Whitecap, and vitamins A, D and E.
- Provide high quality, low fibre (NDF) feed such as good quality silage or grain.
Speak to an Elders Livestock Production Advisor for further information.
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Elders provides recommendations to the best of its knowledge and based on assumptions and information which it understands to be up to date, complete and accurate. If you are aware of any error or inaccuracy with the information on which this recommendation is based, you must immediately bring this to Elders’ attention. This recommendation is provided for your use only, and not that of any other third party. In some circumstances, the information Elders provided may be in summary form or derived from information sourced from third parties, however, Elders has not independently verified the information and cannot guarantee its accuracy.
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