The average human being has an absolute body temperature of 98.6 degrees Fahrenheit. Chickens are different—each bird has an internal temperature that varies greatly. A chicken’s temperature range depends on the ambient temperature as well as factors such as the chicken’s age, breed, gender, activity level and state of health.
Hatching & Brooding Temperatures
A chicken’s temperature variability begins from the time the embryo starts developing within the egg. Largely because of moisture evaporation, the temperature inside an egg at the start of incubation is slightly below the incubator’s air temperature of about 100 degrees. Halfway through development, the embryo produces metabolic heat that raises its temperature to slightly warmer than air temperature.
When the chick hatches, its body temperature is about 103.5 degrees. While the chick’s metabolic systems are developing, its body has little by way of internal temperature control. If the environmental temperature is too cool or too warm, the chick will experience stress, poor growth or even death.
The general rule is that for the first week after hatching, chicks are comfortable at a brooding temperature of 90 degrees. As chicks grow and their internal temperature increases, they need gradually less external heat to remain comfortable. Brooding temperature should be reduced approximately 5 degrees per week until the brooder temperature is the same as the ambient temperature or 70 degrees, whichever comes first.
Rather than using a thermometer, a more practical method of measuring brooding temperature is to monitor the chicks’ body language. Chicks crowding close to the heat source and peeping shrilly are too cold. They might develop sticky bottoms or pile up and smother one another.
Chicks crowded away from the heater and panting are too hot. If
the temperature rises enough to increase their body temperature above 117 degrees, chicks will die. Chicks that are evenly distributed under the heater during sleep, or distributed throughout a brooder while active, are perfectly comfortable.
During the first few weeks after hatching, a chick’s body temperature gradually increases until it reaches a stable 106 degrees, the average temperature of a mature chicken. At this point the chick’s developing metabolic processes let it start regulating its own temperature, which is why brooding temperature should be gradually decreased.
Exactly how long growing chicks need auxiliary heat depends on the ambient temperature, the number of birds in a given space and the breed’s growth rate. In warm weather, chicks might need heat for only three weeks or even less. In cold weather, they might need heat for six weeks, or until they grow enough feathers to regulate their own body temperature. Body language, again, is the key to gauging chick comfort.
The core, or deep body, temperature of a fully feathered chicken normally ranges between 105 and 107 degrees, averaging 106 degrees under normal circumstances. Sometimes the upper limit is as high as 109 or even 113 degrees. The reason has to do with the increased growth rate of modern Cornish Cross broilers compared with a decade ago. Their daily feed consumption has increased and so has their metabolic heat production. As a result, they are more susceptible to heat stress than other chickens.
So how do you take a chicken’s temperature? You can use a digital thermometer—such as Omron 246—inserted about an inch into the chicken’s vent until the thermometer’s beeping indicates it has reached a constant reading. Or you can use an infrared ear thermometer—such as Braun Thermoscan5 IRT6500—placed against the chicken’s featherless facial skin but not on the comb or wattles. The chicken’s skin temperature will be about 3.5 degrees lower than its core temperature.
A chicken’s temperature doesn’t help much in diagnosing illness unless you know the bird’s normal temperature. Further, a chicken’s temperature varies with circumstances. In each of the following pairs, the first chicken typically has a higher core temperature:
- mature chicken—hatchling
- active chicken—resting chicken
- well-fed chicken—hungry chicken
- chicken on the floor—chicken in a cage
- in warm weather—in cold weather
- during daytime—during night
- small breed—large breed
The naturally high body temperature of chickens in general lets the birds self-regulate during seasonal temperature changes. When the temperature drops, a chicken’s body speeds up metabolism to keep the bird warm and active. Chickens therefore suffer less in cold weather than in hot weather and are less apt to die from cold stress, provided they have adequate nutrition and drinking water, and their housing is neither damp nor drafty.
In warm weather, a relatively high body temperature makes it easy for the chicken to release body heat into the surrounding air. When the bird inhales, its air sacs draw air deep into its body. Exhaling releases body heat, but only if the ambient temperature is lower than the chicken’s body temperature.
A chicken’s body typically operates most efficiently—that is, requires little energy for temperature regulation—at environmental temperatures between 70 and 75 degrees. This temperature range is optimal for good health, active foraging and sound sleep.
At temps reaching 15 degrees above and below this range, a chicken stays comfortable through behavior modification. This still allows the chicken to maintain a comfortable body temperature without using a lot of energy.
Chickens that are on the cool side eat more, ruffle their feathers to trap warm air and huddle together for warmth. Chickens that are on the warm side eat less, lift their wings and move away from each other to improve airflow.
A fully feathered chicken benefits from temperature fluctuations of as much as 15 degrees on either side of optimal, because the changes help the bird’s body acclimate to seasonal temperature changes.
Extreme temperatures, however, result in cold stress or heat stress, because they require a chicken to use energy that would otherwise go to maintaining health and productivity. A cold-stressed chicken covers its legs and shivers. Hens stop laying. If the chicken’s core temperature drops below 73 degrees—which can happen when the ambient temperature hovers around 25 degrees—the chicken will probably die.
Because a chicken’s core temperature is already high, heat stress is more difficult to deal with than cold stress. A heat-stressed chicken drinks more—causing loose, watery droppings—pants and vibrates its throat muscles (called “gular flutter”) to increase evaporation of warm body moisture. A chicken that can’t maintain its core temperature below about 115 degrees might die. A mature chicken that is acclimated to warm temperatures pants less readily and is less likely to die at what might otherwise be a lethal temperature.
The likelihood of a chicken dying from heat stress depends on many other factors, including the bird’s age and size, how rapidly the air temperature rises, how high it goes, how long the weather stays hot, and how humid the air is. Factors that help chickens survive a hot spell include the birds’ ability to get out of the sun, the presence of air circulation (if no breeze, then from a fan), and access to plenty of cool drinking water.
Help Chickens Stay Cool
A chicken has no sweat glands, so it uses other ways to stay cool. Chickens from hot climates—such as Leghorns and other Mediterranean breeds, as well as the Fayoumi, which originated in Egypt—have large combs and wattles, through which blood circulation increases in hot weather to help dissipate body heat. Because feathers trap heat close to the body, another warm-climate adaptation is sparse body feathering and no feathers on the legs and feet.
Loosely feathered breeds such as Orpingtons and heavily feathered breeds such as the Asiatics (Brahma, Cochin, Langshan) and Americans (Plymouth Rock, New Hampshire, Rhode Island Red) suffer more in hot weather than the lightly feathered breeds. Hens of any breed that are laying suffer more than those not laying.
When the ambient temperature reaches 104 degrees Fahrenheit or more, most chickens can’t lose excess heat fast enough to maintain a comfortable body temperature. The following precautions minimize heat stress by helping chickens cool down in hot weather.
- As water consumption increases, increase the number of waterers.
- Frequently fill waterers with cool water, or add ice.
- Keep water cool by placing drinkers in shade.
- Add electrolytes to the water to replace those depleted because of the heat.
- Avoid otherwise medicating the water; birds that don’t like the taste will drink less.
- Keep rations fresh by purchasing feed more often and in smaller quantities.
- Distribute feeders so no chicken must travel far to eat.
- Turn on coop lights for a while before dawn and after dusk to encourage eating during cooler hours.
- Open windows and doors or install a ceiling fan to increase air circulation.
- Reduce crowding by moving some birds or expanding their housing.
- Do not confine chickens to trap nests or cages in sunlight or where ventilation is poor.
- Provide shady areas where chickens can rest; if necessary, use a tarp or awning.
- Fill a wading pool with cool water for the chickens to stand in.
- If humidity is low, hose down the coop roof and outside walls several times a day.
- Lightly mist adult birds. (Never mist chicks, though, as they chill too easily.)
- Insulate the coop roof to reduce radiant heat from the sun.
- Do not disturb your chickens during the heat of the day.
This story originally appeared in the July/August 2018 issue of Chickens magazine.