I remember sitting on my parents’ front porch in late afternoon during the dog days of summer. This can be a rough time for people, pets, and especially chickens. Heat affects our chickens and that means there are steps that can be taken to mitigate this and keep them healthy and as happy.
First, you need to know about the thermoneutral zone (TNZ). The TNZ is the ambient temperature at which an animal is neither hot nor cold, like being in a room and neither sweating nor shivering. When a chicken is in the TNZ, it is not having to alter its basic metabolic rate or behavior to maintain body temperature.
At different ages, this zone can be drastically different. For a day old chick, its TNZ is going to be somewhere in the mid- to lower-90s F., while a mature rooster’s might be in the 65° to 75° F. range.
What does this mean? A chicken experiencing overheating will lower its metabolism, it will pant (gular flutter) and spread its wings out to release body heat. Panting also releases significant amounts of body water into the air, eventually causing dehydration and pH imbalance. Slight, short deviations from the TNZ will have no lasting effect on a chicken, but prolonged excursions into the zone can reduce hatchability, egg shell quality, egg production, feed conversion, growth rates, and—if exposed long enough—death.
Secondly, let’s look at what happens to production as ambient air temperature rises. For this example, we will say the chicken’s ideal temperature is between 65° and 75° F. Between 75° and 85° F. we can notice a decrease in feed consumption, egg size, and shell quality may suffer. At 85° to 90° F. feed consumption falls even further, and weight gain is significantly lower. We will see a decrease in egg production.
As temperatures continue to rise closer to 100° F. egg production and feed consumption will be severely reduced, while water consumption will be extremely high. We can also see heat prostration or heat exhaustion. Air temperatures above 100° F. are extremely dangerous, at this point emergency measures may be needed and survival is the major concern.
A chicken loses body heat through four different ways: radiation, conduction, convection, and evaporation. When a chicken is in the TNZ, it dissipates heat through the first three methods—from the comb, wattles and other non-feathered areas (i.e. under the wings). This is known as sensible heat loss, and the bird does not have to alter is normal behavior.
Once ambient temperatures increase, heat loss shifts from sensible to evaporative cooling. As the bird pants, heat is removed by the evaporation of water. The downside to this is that the bird is eliminating water from its body. During panting, the bird also releases substantial amounts of CO2, so much so that prolonged periods of panting can lead to loss of electrolyte balance. A change in blood pH of only a few tenths of a point can be fatal.
Fortunately, we can mitigate heat stress. First and foremost, you must have good, clean, cool water available at all times. Water should be kept out of the sun, in a cool place.
Warmer water is less effective in cooling the chickens and can lead to a rapid buildup of fungi, mold, bacteria, and other microbes. Cooler water temperature can remove some body heat, and any moisture loss due to panting can be replaced.
Electrolyte solutions can be added to the drinking water to help mitigate some of this loss. The added electrolytes will replace the ones that have been lost and restore pH balance, and will also stimulate water consumption.
Chickens should also be fed during the cooler parts of the day, such as very early in the morning. When chickens digest feed, their metabolism increases, producing heat and therefore increases in their body temperature.
Check the roof of your coop. Is it bright and shiny or dull? A bright, shiny roof will reflect much more sunlight and heat than a dull or dusty roof…and lower coop temperature by several degrees.
Regularly remove litter, as decomposition of built-up litter can produce heat through microbial decomposition. Removing litter also reduces moisture in the coop, potentially lowering relative humidity. Plant grass around the house, as grass can absorb heat from the sun, whereas bare ground can actually reflect heat into the house.
Another source of reducing heat—and possibly the greatest—is through proper ventilation. The best and most effective method of cooling poultry houses is through air movement and wind-chill.
Air movement displaces hotter, moister air from the house and replaces it with cooler, drier air. As birds breathe, excrete waste, and water evaporates from the drinkers (if using an open bell-type drinker) the relative humidity in the house will increase, making the temperature feel even warmer and reducing the effectiveness of panting. A proper ventilation system will remove hot air and humidity.
Creating moving air can be done naturally or artificially. For natural ventilation and air movement, prevailing winds of the area can move air in and out of the house. To do this requires a little planning ahead. Thinking about your farm, which way does the wind typically blow? Does it blow west to east or north to south or any other direction? Once you know the direction, your coop can be oriented to allow for maximum air flow.
You will want to install windows on the sides with the prevailing winds and on the opposite side of the house. For instance, if the wind blows primarily west to east, you would want to install windows on the west and east sides.
Artificial ventilation requires installing fans to pull or push air through the house, and would be somewhat impractical for small coops. If going this route, your best option would be a window fan that would help pull air through the coop. You can also mount a wind turbine on the roof of the house. When the wind is blowing these can generate a significant amount of air flow.
How much ventilation do you need? Probably more than you think. For winds below 5 mph, there is really no felt difference, but a 10 mph wind velocity can decrease temperature by about 10° F. A 10 mph velocity would be considered a gentle breeze—small flags will be extended and leaves will rustle.
Openings in the coop should be at least 1’ x 3’ to allow for sufficient amount of air movement.
Even though its summer and temperatures are on the rise, there are some very easy and effective ways to help your chickens manage their body temperatures. Remember, the key is keeping your chickens in their TNZ. Keep them comfortable and you will reduce stress and increase productivity and health of your flock.