The subject of this article is high-producing dairy cows. However, the general concepts are broadly applicable to all livestock - with some obvious considerations around the practicality of some of the management actions producers can implement.
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With the prospect of another long, hot summer in front of us, what can you do to minimise the impacts on your cows?
Heat stress can have a very significant impact on your dairy cows, and ultimately your farm income.
Heat stress can:
- Reduce milk production by up to 40 per cent in severe cases (and this lower production can last for several weeks).
- Reduce milk protein and fat tests.
- Reduce feed intake, with impacts on body condition.
- Impact cow health and fertility.
- Increase the risk of disease such as mastitis.
Dairy Australia has an excellent publication, 'Cool Cows - strategies for managing heat stress in dairy cows'.
The booklet provides a wealth of information to allow dairy producers to recognise the signs and effects of heat stress. It also gives strategies that can reduce its impact.
While we might associate heat stress with temperatures above 40 degrees, even at temperatures above 25 degrees, cows begin to feel uncomfortable, and will burn energy to keep cool. Sweating is responsible for 70 per cent of the heat loss from cattle, with the other 30 per cent mainly from breathing, with a small amount lost from the skin and saliva.
So, anything that can be done to help cows lose heat through evaporative processes is worthwhile.
What can you do to monitor and implement strategies to reduce the impacts of heat stress?
- Monitor cows' breathing rate - 40-60 breaths/minute is normal, above 60 indicates the cow's core body temperature is above 39 degrees, and above 70 indicates significant stress. 90-100 breaths/minute can result in cow death.
- Use forecasts and other tools to anticipate the onset of heat.
- Provide shade - it can reduce radiant heat loads by more than 50 per cent.
- Provide cool, clean water. High-producing cows may consume up to 250 litres of water per day in hot conditions. The greater the difference in temperature between the environment and the water, the better the result.
- Sprinklers and fans.
- Minimise walking time.
- Take feed to cows sheltering from heat.
- Modify milking times - milk as early as possible in the morning, and after 5pm in extreme conditions.
Other basic principles to remember are:
- Flow rate to troughs is more important than the capacity (volume) of the trough.
- Don't run black polypipe to troughs along the ground.
- Ideally, place troughs in shaded areas.
- Place troughs away from feed.
- Troughs should be cleaned frequently - drainage water needs to be directed away from the trough.
In our environment, heat stress can have significant impacts on cow health and performance, and on your financial performance as a dairy producer. Investing in keeping your cows cool will have a significant pay-off.
Producers are encouraged to review the information provided in the 'Cool Cows' publication and speak with your farm advisors.
