When we're in the depths of winter, it's easy to forget how hot it can get in the summer.
But learning about how heat affects chickens is a potential life-saver - and it's never too early to start thinking about it.
Because the fact is that heat exhaustion and heat stroke are killers which can creep up very quickly if you're not clued into what the signs are.
In this article, we'll look at how to tell if your flock is becoming badly affected by the heat.
From there are some easy steps you can take to make sure that you care for your girls (and boys) equally as well in the heat of summer as the cold of winter.
Why is recognising heat exhaustion important?
A chicken's normal body temperature(1, 3) is between 40ºC and 41ºC (104ºF and 107ºF). They don't have sweat glands, so there are limits to a chicken's ability to regulate its body temperature.
Cold isn't really a problem for chickens - they have feathers to protect them - and tend to do well in the winter - even in very cold climates.
But heat can be a very serious issue.
It's in those circumstances you should be aware of the signs of heat exhaustion and know how to deal with it.
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Some breeds can deal with extremes of temperature better than others(2).
Breeds originating in cooler, more temperate climates have more difficulty in dealing with extremes of temperature. This is an important factor when considering ways of managing heat stress.
Older chickens can sometimes adapt if the temperature rise is gradual, but if it's quick they won't be able to. They're likely to suffer most.
Heavy breeds will be next in line. Broilers - birds bred for their meat - will show signs of heat exhaustion much more quickly than layers.
And broiler chicks (between 6 and 8 weeks old) have been shown to be even more badly affected by heat exhaustion than adults(4).
The first and most obvious sign of heat stress.
When the environment is hot the chicken needs to lose heat or its body just keeps heating up. The feathers, which are so efficient at keeping warmth in the body in the winter, also prevent heat escaping in the summer.
The chicken needs to cool off by evaporation.
Because a chicken has no sweat glands, she loses the water from its respiratory system - in other words she pants to keep cool.
A panting bird will be very obvious - there is no noise coming from its beak, only moist air.
This is related to panting and happens particularly when humidity levels are high.
Because the air the hen is breathing out is full of moisture, it becomes harder to expel it if humidity levels are high. To compensate, the hen's breathing increases from about 20 to as much as 240 breaths per minute.
This then becomes a kind of vicious circle. As breathing becomes quicker, the bird is using up more energy and that itself produces more heat.
So the problem can escalate very, very quickly.
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This one is the silent killer.
It's not something which can be seen, but loss of moisture from the body results in a loss of electrolytes which the chicken needs to remain healthy.
Think of them as the energy in the battery which keeps your chicken going - a kind of chicken Gatorade.
Depletion of electrolytes can cause the kidneys to malfunction, the immune system to weaken and diseases to take hold - in particular respiratory disease.
It also depletes calcium stores, and can create related problems, including soft-shelled eggs (see no. 8 below).
For all those reasons - and also because electrolytes can help weak baby chicks - I keep a ready store of electrolyte powder in my chicken first aid kit and add it to drinking water when temperatures soar.
This happens as the bird tries to expose more skin to cooler air, rather than have feathers trap the heat.
You'll often see this in hens who are dust-bathing. In lower temperatures birds will just hold the wings out from the body. As temperatures rise it can look as though they're dragging one or both wings on the ground.
A panting bird can't eat as much as it should - it's as simple as that.
Chickens (like most animals) tend to eat less in hot weather anyway. But watch out for your feed not being used in anything like the same quantities as usual. And keep an eye on individual birds to make sure they're getting some food.
In terms of drinking water, if you use a product like The Chicken Fountain this won't be an issue since it provides a constant supply of water direct from your mains.
But if your waterers are the more usual type then you will see them empty very rapidly. Chickens who are over-heated will drink somewhere between four and five times their usual amount.
This is directly related to drinking more - the birds' output is likely to be much more liquidy than usual.
Why does this matter? More liquid loss equals yet more electrolyte loss, weakening of the immune system and consequently more susceptibility to disease.
It's hardly surprising really, is it? Think about how you feel when the weather is very hot.
Your hens are losing electrolytes, not eating much - if anything - and expelling a lot of waste products which are dehydrating them even more.
At this point chickens are certainly showing fairly severe symptoms of heat exhaustion.
By now, the body's balance is disturbed.
Food consumption is down, the chicken is working harder to breathe and expelling more waste products than usual. The body needs to use its own stores of protein, fats and carbohydrates to get by.
The hen no longer has enough calcium supplies to lay - or if she does, you'll see the number of thin- or soft-shelled eggs increase.
And that, of course, carries its own dangers.
Never seen a soft-shelled egg? Here's a short video from a friend of mine, Tim Daniels of PoultryKeeper.com, showing what they look like.
By this stage, a chicken will be very severely dehydrated. Immediate action is required if there is to be any hope of saving her.
The bird's system is collapsing and death will not be far away.
By this stage there is no helping a chicken suffering from heat exhaustion. The loss of water and electrolytes disturbs the chemical balance so badly that the heart and lungs cannot cope and stop functioning.
Clearly, your aim is to look for and treat symptoms long before this point is reached.
Of course. You'll find detailed information in my article about how to keep chickens cool. Here's a quick guide of easy steps to help prevent the problem.
1. Always provide lots of water in different places around the chicken run.
2. Starting the day with a block of ice in the waterer means the liquid will keep cool longer.
This is a short video with 5 simple, inexpensive tips for you to action right now, which will help keep your chickens well hydrated during the heat of the summer months.
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This is the article about a home made electrolyte drink which I refer to in the video.
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3. Provide plenty of shade. Plant trees and, while they're growing, add a tarpaulin to your run where the flock can cool off. Make sure it's UV resistant. (This doubles up in the winter as a wind-break).
4. Help them keep cool by providing a dust-bathing area.
5. Keep a store of poultry electrolytes, or make your own.
6. Avoid high protein foods, and do not use apple cider vinegar in the heat. Both increase metabolism and will add to the problem rather than helping it.
7. Provide low fat food with a high water content such as watermelon, and have some frozen treats ready made to make sure your chickens stay well hydrated.
8. Apples have been proven to be a good treat for chickens at times of extreme heat stress. See this article for more details.
Summer time can bring other problems with our flocks. These articles may help you sort some of them out. Just click on the pics.
I make every effort to provide readers of my site with information which has been confirmed by scientific, peer-reviewed research, particularly where health issues are concerned.
For this article, some of the most helpful sources are:
1. Borges, S.A., et al: 'Physiological responses of broiler chickens to heat stress and dietary electrolyte balance'. Pub. Oxford Journal of Poultry Science, 2004.
2. Gail Damerow: The Chicken Encycolpaedia: an Illustrated Reference.
3. Rural Chemical Industries Ltd: 'Thermoregulation in poultry'. Pub. Heatstress in Livestock.
4. Tirawattanawanich, C., et al: 'The effects of tropical environmental conditions on the stress and immune responses of commercial broilers, Thai indigenous chickens, and crossbred chickens'. Pub. The Journal of Applied Poultry Research, 2011.