What is Cold Stress in Poultry?
by Alexa Lehr | The Pioneer Chicks | January 2, 2024
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What is cold stress in poultry? Cold stress is the response a chicken’s body has to staying warm in cold weather. It is an issue that is often overlooked since chickens generally handle cold temperatures better than hot temperatures. However, cold stress can be just as dangerous and deadly as heat stress. Being concerned about your chickens staying warm during the winter is legitimate. But you should make sure you are taking the correct precautions to help them stay warm and not following bad advice. I used to think that my chickens were just fine in cold temperatures, but I have since learned that the cold weather does affect them. Understanding how cold stress works is essential for knowing how to properly prevent it in your homestead flock!

What is Cold Stress in Chickens?

Simply put, cold stress is any stress that a chicken’s body experiences due to dealing with extremely cold external temperatures. Cold weather stresses all the systems in a chicken’s body… the circulatory system is restricted, the digestive system is inhibited, and the immune system is suppressed.

Chickens, like other birds, have a high core body temperature of around 105-107°F. This high core body temperature is detrimental during the summer, when chickens are trying to get rid of excess warmth. However, during the winter it allows chickens to stay active despite cold temperatures. Since chickens can handle cold temperatures better than warm temperatures, cold stress is often overlooked. I know when I first started raising chickens I thought that as long as I chose cold hardy breeds and winterized the chicken coop properly, that my flock would be fine. I have since learned that chickens are way more affected by cold temperatures than I first thought!

BUT… most cold hardy chicken breeds have a pretty low cold weather tolerance. Just because it feels cold out to us, doesn’t mean it is cold enough to cause serious cold stress for our chickens. There is both ‘healthy’ cold stress and dangerous cold stress that chickens can experience. To help you understand how cold stress works, you must learn what causes cold stress in chickens.

Fun Fact: Chickens have a very high blood pressure because of their high body temperature! This high blood pressure allows them to stay active all day long, just like their ancestors would have had to do in the wild.

What Causes Cold Stress in Chickens?

Increased Energy Needs:

Cold stress occurs when chickens have to expend much more energy than normal to go about usual activities. Since chickens have such a high body temperature, they perceive coldness differently than humans. An external temperature between 65-75° F is the ideal temperature for chickens to function at while using minimal energy. Cold hardy chicken breeds are more comfortable in a temperature range between 55-65°F.

As the temperature decreases, a chicken will modify its behavior to better conserve energy. When the temperatures get near freezing (32°F) a chicken’s body begins to experience some stress as it has to expend more energy to stay functioning. The temperature at which a chicken starts to experience stress is called the critical low temperature.

This critical low temperature for each chicken will vary. Factors that influence an individual bird’s critical low temperature include how long the chicken has been able to slowly adjust to the colder temperatures, the breed of chicken, and the age of the chicken.

Drastic Temperature Changes:

Another cause of cold stress is drastic changes in the external temperatures. A gradual decrease in external temperature allows chickens to acclimate to the colder weather. However, mother nature does not always play along, and weather patterns and temperatures can fluctuate greatly during northern winters. This is when cold stress is really accentuated.

Depending on how rapidly the weather changes and how long the extreme temperatures last will affect how much cold stress your flock experiences. The critical low temperature is determined by how much a flock is able to acclimate to temperature changes.

Other things that affect how much cold stress a chicken experiences include:

• age- very young chickens and very old chickens experience more stress quicker
• weight– an underweight chicken experiences more stress sooner than if it was at a healthy weight
• diet– a diet that does not provide the energy and protein needed during the winter will cause a flock to experience more stress
• health- chickens that have a disease or have parasites will experience stress sooner than healthy chickens
• humidity- high levels of moisture in the air makes it harder for chickens to stay warm, which causes stress
• exposure- blowing winds, drafts, and exposure to rain, sleet, and/or snow will chill chickens and cause stress

How Does Cold Stress Affect Chickens?

So, you know what cold stress is, you know what causes it, and you know that the critical low temperature plays a role in accentuating cold stress, but how else does it affect chickens? Cold stress can have detrimental affects on the health and well-being of your flock. Not only does it mean a chicken is cold, it also negatively affects the immune system and overall health of a chicken.

It causes ruffled feathers…

If a chicken is exposed to sudden cold temperatures or is exposed to cold temperatures for a long time, cold stress kicks in. A chicken’s first line of defense against the cold is its feathers. The feather follicles that the feathers grow from can be turned upward, causing the feathers to have gaps between them. The air trapped between those gaps is warmed by the chicken’s body and helps insulate the chicken.

Under minor cold stress, a chicken can stay warm enough by conserving energy and fluffing up its feathers to conserve body heat. During times of severe cold stress, the simple behaviour of fluffing up the feathers is not enough. The chicken cannot generate and trap enough heat within its feathers to stay warm.

Tip: Check out this article to learn How to Recognize Cold Stress in Chickens.

Which then leads to reduced circulation…

If the temperatures continue to drop, a chicken will begin to restrict circulation to its comb, wattles, and feet. This restricted circulation helps conserve body heat but also opens up those extremities to frostbite. To compensate, chickens hunker down or perch to cover their feet with their breast feathers. They will also huddle together to conserve body heat as a group. The reduced activity also allows them to save on energy, which they can then use to stay warm.

Reduced circulation is a result of cold stress and usually one of the first actions that the body takes to conserve energy and focus on keeping the important systems warm and functioning.

Tip: Adding fresh ground ginger to your flock’s diet can stimulate healthy circulation!

And can progress to shivering…

Chickens can also shiver, which increases their metabolic rate. The increased metabolism requires more energy, which means higher feed intake. Since calories are so important during the winter, a chicken who goes off its feed will regress quickly. If a chicken goes even a single day without food during cold temperatures, its body temperature will decrease by 2.5°F.

A chicken is trying to avoid the lethal core temperature of 73°F. While it may seem like a far stretch, from 105°F to 73°F, a chicken’s body temperature can decrease quickly when not enough energy is present and the temperatures are extreme.

Remember, chickens use up to 75% of the energy they consume just for normal body functions of digestion, circulation, and respiration. That leaves only 25% of their daily energy for other activities such as staying warm, reproducing, and other poultry activities. Shivering will use up that extra energy and may even draw on reserve resources of energy to keep the bird warm. This can lead to a stop in laying, weight loss, and an overall health decline.

Tip: Make sure your flock has acces to a high-protein, complete feed at all times during the winter to provide them with energy and fuel for staying warm.

It can also cause enzyme reduction…

A chicken’s metabolism is negatively affected by cold stress as well. The process of metabolism is fueled by enzymes, which are proteins. Enzyme levels are affected by extreme cold and are used up faster by the body. When enzymes are decreased, they reduce the effectiveness and efficiency of digestion. A suppressed digestive system means the chicken can’t utilize the energy from its food as well. Keeping enzyme levels steady during the winter is important for proper energy levels to be obtained for staying warm.

Tip: Feed high-protein, natural treats (like black soldier fly grubs) on a daily basis to add supplemental protein to your flock’s diet.

And it decreases immunity…

Due to the affect that cold stress has on enzymes, it also affects a chicken’s immune system. The immune system is the line of defense against diseases and parasites. When a chicken’s immune system is suppressed, it can’t fight off harmful pathogens or keep parasite levels in balance. Cold stress can lead to oxidative damage to different organ tissues when the antioxidation system is out of balance as well.

Tip: Use dried elderberries to boost flock immunity during the winter!

Addressing Cold Stress in Chickens

You know all about cold stress now, but how can you tell the difference between when a chicken is cold and when it is experiencing cold stress? Just because a chicken looks cold does not mean it is suffering from cold stress. It may be experiencing some stress, but don’t we all feel a little stressed when we are cold? Also, small amounts of cold stress are not a huge problem. It’s when cold stress becomes accentuated or is present for long periods of time that it can take a toll on the health of your flock.

The main key to recognizing when cold stress may be an issue is monitoring the weather. Sudden changes in the temperature and prolonged periods of extreme temperatures will be when cold stress should become a concern. Certain breeds may be more prone to cold stress than others, however, most cold hardy breeds have a higher tolerance of cold weather and don’t experience the stress as rapidly as fair weather breeds.

Make a Cold Stress Plan

Recognize where the weaknesses are in your flock. Sick, ailing, or injured birds will begin to experience cold stress first. Both internal parasites and external parasites will accentuate stress as well. Keep in mind the different factors that play a role in the critical low temperature for different chickens. Get a general idea of what your flock’s average critical low temperature would be. This would be the temperature that causes the chickens in your flock to start exhibiting signs of severe cold stress. Then you will have a rough idea of when your flock will need the most care to prevent cold stress from becoming a danger to your flock’s health.

For tips on helping chickens deal with cold stress, check out Helping Your Flock Deal with Cold Stress.

Prevent Cold Stress

Take measures to help prevent your homestead flock from experiencing cold stress. Keep in mind the main causes of cold stress: increased energy needs and a drastic change in temperature. To some extent, you can control both of these causes. During cold winter weather, your flock’s energy needs will increase and their diet should reflect that. Keep an eye on the weather and plan ahead of time for when severe cold weather hits.

Here are some measures you can take to prevent cold stress in your flock:

• winterize the chicken coop
• monitor dietary protein levels
• adjust winter diet rations
• find ways to help your flock stay warm

The fact still stands that chickens can handle cold weather better than warm weather. However, cold stress is still an issue to be addressed during the winter. Cold stress decreases immunity, reduces nutrient absorption, and uses up lots of energy. It can have negative effects on the homestead flock if the proper pre-cautions are not taken. Hopefully you are now more aware of how cold stress affects poultry and what you can do to help your flock stay healthy, happy, and stress-free this winter!

Make sure you get a copy of our ebook, The Complete Guide to Winter Chicken Keeping so that you can take the best care of your flock this winter! It contains great information for preventing and dealing with cold stress in your flock.