It’s the hot season again! That time of the year when poultry farmers face challenges in managing their flocks. During this season there is a high mortality rate among chickens as a result of heat stress.

Lack of adequate knowledge of heat stress is the leading cause of the high mortality rate among chickens in the poultry industry for many Zambians. In this article, we talk about what heat stress is, its causes, and how to identify it in chickens.

What is heat stress?

Chicken bodies have a natural tendency of generating heat as a way of keeping the bird warm during cold times, and this continues even in hot seasons.

During the hot seasons, chickens strive to keep their bodies cool to maintain temperature balance from the inside. However, they fail to do this when they are exposed to a high temperature than normal. The body will keep on generating heat while the outside environment is hot. Consequently, this will cause a high-stress build-up in temperature from the inside.

Heat stress is a condition in which a bird’s core body temperature increases extremely to the extent of causing harm to the bird. Therefore, if you can’t detect heat stress early and treat it, it can lead to the following problems for a poultry business:

1. Reduced Egg production

Heat stress is usually accompanied by dehydration. This means the bird has less water in the body. This prevents the proper formation of eggs as the contents of an egg are mainly in liquid form.

Hens may completely stop laying or if they lay, eggs will be very small compared to their normal size. Furthermore, the shell quality is equally affected causing hens to produce less dense and light eggs.

2. Meat/ weight shedding

For broilers the bigger the bird, the more meat it has. The size of the bird determines the price for that particular bird because clients prefer chicken with high meat content.

The fact that heat stress causes dehydration, there is a reduction in the various chemical reactions such as digestion and nutrient absorption. This further reduces the growth of the bird leading to stunted growth and lightweight production.

3. Loss of appetite

As a way of reducing heat exhaustion, chicken often reduces feeding and increases drinking more water. Digestive processes generate heat and increase the core temperature of the body thus, less food intake slows down these processes and generates less heat.

Here, it’s quite evident that the more our chickens feed, the bigger they grow, the higher their value, and the more they lay eggs in case of layers.

Therefore, a decrease in food intake may come with many consequences for the poultry business.

You might also like: 5 Common chicken diseases and how to prevent them

What causes heat stress?

Most poultry farmers in Zambia underrate the impact of heat stress, as they pay less attention to this particular issue.

Once a time I visited a friend who happens to own a chicken coop for broilers. He invited me at the time when he was about to refill the feeders in his chicken coop so I offered to help.

The coop was about 2 by 4 meters in size so I wasn’t expecting a large number of birds inside, to my surprise, I found so many chickens squeezing in this small room. I asked how many birds there were, and he said: “Initially there were 60 birds, but as time passed they died out one by one and so far there are only 42 birds.”

The interior atmosphere of the coop was so hot that it was unbearable for me as a human to spend even 5 minutes inside.

If as a human I couldn’t bear to withstand the heat in a chicken coop for that long, what about those poor birds in there? I may not be sure why the chickens were dying but I’m very sure heat stress was one of the reasons.

At the end of the rearing period, this person had fewer chickens to sell. A situation that he would have avoided.

The following are some of the reasons why heat stress occurs:

Extra stress: Activities such as chasing the chicken by humans, dogs, and cats may cause it to generate more heat from the inside which may raise its core temperature.

Overcrowding: Chicken coops need to have enough space for chickens to freely roam around, this enables a cool breeze to flow through. Overcrowding may encourage heat spreading among the birds thereby raising the temperature even higher as they rub against each other.

Lack of proper ventilation: Proper Ventilation is important for the easy exchange of gases. Air needs to freely enter and exit the coop frequently. Inadequate ventilation means less access to fresh air and this leads to the internal environment heating up raising the temperature among the birds

Related Article: How to get your chickens to mate

How can you identify heat stress in chickens?

The following symptoms indicate heat stress in birds:

• Panting: opening the beak and breathing heavily
• Elevating wings: wings are partially spread hanging them away from the chicken’s body to release the heat.
• Dry and pale combs and wattles: combs and wattles are a major heat-releasing feature for chickens and pale red combs may signal a problem.
• Appetite loss
• Frequent sand bathing
• Failure to properly stand

Once you detect these symptoms, you should implement measures of treatments to reduce this effect the soonest. As humans, we often wear light clothes, seat outdoors under sheds, swim in pools, and take cold drinks in summer.

For chickens, the body comes with an already made body warming mechanism (feathers) which cannot be stripped off or changed into something light, there is no bathing and swimming in pools.

This means their normal body temperature is higher than humans or other animals. Therefore, to avoid heat stress, it is important that their environment is regulated as much as possible to suit their body temperature need.

In the next article, we discuss how to treat and prevent heat stress