Akash Wadal

Department of Animal Nutrition,

College of Veterinary Science and Animal Husbandry,
Acharya Narendra Deva University of Agriculture and Technology
Kumarganj, Ayodhya-224229

The summer season brings with it several days with high ambient temperatures, frequently coupled with high relative humidity. Extreme heat can have a significant impact on a flock’s productivity. In less extreme temperatures, heat stress is frequently disregarded as a cause of poor growth or modest reductions in egg production and shell quality. However, at environmental temperatures exceeding 33°C, substantial mortality and significant output losses are clearly visible.

The combined effects of temperature and air relative humidity on a bird are known as heat stress. The term “effective temperature” refers to this. In any temperature, higher air humidity will result in more pain and heat stress for birds. Producers need to keep a close eye on the local humidity and temperature. In general, the temperature rises, and the relative humidity falls during the day. When there is less humidity, evaporative cooling—which includes cool pads, misters, and foggers—is the most effective way to stay cool.

Foggers add humidity, which can exacerbate heat stress during the evening when temperatures drop, and humidity usually rises. In open housing, more air flow with fans alone will lessen heat discomfort when humidity levels are high. The wind chill effect is caused by air movement and is the body’s perception of a drop in atmospheric temperature.


Excess body heat is removed by four different mechanisms.


Body heat is lost to the cooler surrounding air. Birds will droop and stretch their wings to maximize exposed  surface  area.  Convection  helps  with  air  flow  by  producing  a  wind  chill  effect.

Vasodilation – swollen wattles and combs transport internal body heat to the surface, where it is lost to the cooler surrounding air.


Electromagnetic waves carry heat through the air to a distant object. Body heat is transmitted to cooler things in the home (walls, ceiling, and equipment).

Evaporative cooling.

Rapid, shallow, open-mouth breathing leads to increased heat loss by evaporation of water from the mouth and respiratory tract. Lower atmospheric humidity promotes evaporative cooling. Conduction

Birds lose body heat when they come into direct touch with chilly items like litter, slats, or cage wire. Birds will seek cooler spots within the house. Birds seek cooler spots by lying on the floor or digging in rubbish.

  • Sensible heat loss includes radiation, convection, and conduction.
  • The  thermoneutral  zone  of  the  chicken  is  typically  between  18  and  25°C.  Within  this temperature range, sensible heat loss is sufficient to keep the bird’s usual body temperature at 41°C.
  • Above the thermoneutral zone, the effectiveness of sensible heat loss mechanisms decreases.
  • At this point, evaporation of water from the respiratory tract becomes the bird’s primary heat loss method.
  • The evaporation of one gram of water removes 540 calories of body heat.At temperatures exceeding  the thermoneutral  zone,  the bird  must  burn energy to  maintain  normal  body temperature and metabolic functions. This diverts energy away from growth and egg production, resulting in reduced performance.
  • Heat stress production losses are based on the

1. maximum temperature the flock was exposed to.

2. The duration of the high temperatures.

3. Temperature Change Rate

4. Relative air humidity


  • During hot weather, closely monitor the flock’s feed consumption. The diet must be rebalanced for other vital elements, including amino acids, calcium, sodium, and phosphorus, based on the birds’ productivity need (i.e. stage of production) and observed feed intake.
  • Insufficient amino acid intake is the leading cause of productivity loss in hot weather.
  • Various measures can be used to regulate excessive temperatures and maintain adequate feed intake.
  • To maximize consumption, avoid feeding during hot seasons and opt for early morning or nighttime hours. Normally, a maximum of one hour is advised for feeder clean-out time, however this can be increased to three hours if the temperature exceeds 36°C.
  • Consider adding a one- or two-hour overnight feeding.  Adjust the feed particle size, either by increasing it or by providing a crumble diet. With crumble diets in laying flocks, an additional source or presentation of large particle limestone is advised.


  • Create diets with easily digested ingredients, especially protein sources. Excess protein metabolism causes the bird to overheat and exacerbate the electrostatic imbalance. Don’t use a high crude protein minimum in the ingredients; instead, formulate to targets for digestible amino acids.
  • Without lowering the quantities of amino acids in the diet, synthetic amino acids can lower the amount of crude protein. Lowering the amount of heat produced by digestion in the body can be achieved by increasing the percentage of energy coming from highly digestible fat instead of carbs or proteins.
  • When dietary fat is digested, this phenomenon, known as heat increment, is at its lowest. Because of the increased excretion of urine under heat stress, the requirement for phosphorus increases. Under circumstances of heat stress, increases of up to 5% ought to be suitable.
  • In hot weather, the goal dietary electrolyte balance (molar equivalency of Na+ + K+ – Cl-) should be approximately 250 meq/kg.
  • The ratio of chloride to sodium in the diet should be between 1:1 and 1.1:1. Higher salt levels (0.02-0.03% more than in non-heat stress settings) may be necessary in hot weather due to increased electrolyte loss. Additionally, care must be taken to ensure that the birds are not receiving an excessive amount of chloride from the water.
  • Vitamin and trace mineral consumption is also decreased as a result of the decreased feed intake. Several of these micronutrients, especially antioxidants and B vitamins, may help the bird while it is under heat stress.
  • To enhance performance, supplement the diet with 200–300 mg of vitamin C per kg of body weight.
  • Since organic zinc is a crucial mineral component of the enzyme carbonic anhydrase, it may enhance shell quality by supporting the enzyme’s activity. By lessening the antagonistic unfavorable interactions that occur during digestion between zinc sources and inorganic copper, organic copper may also be beneficial.
  • Nicarbazin, an anticoccidial medication, should not be taken in hot weather as it can raise the risk of heat stress-related death.


  • Before the summer heat arrives, the ventilation system should be inspected to ensure proper functioning.
  • Make sure the fan shutters are clean and working. During times of high temperature, fan belts should be replaced or adjusted to prevent sliding. To provide the necessary airflow for ventilating the house in warm weather, there must be sufficient air inlets.
  • The fans will be turned down and the airflow will be reduced by insufficient inlet space.
  • Everything that could obstruct the passage of incoming air should be kept out of inlets and kept clean.
  • Turn incoming air onto the birds by using baffle boards. The accuracy of thermostats has to be verified. To providing backup power during hot weather, an auxiliary power system needs to be installed.
  • To guarantee sufficient and consistent airflow, check the static pressure settings in the home’s positive and negative pressure ventilation systems (12.5–30 Pa or 0.05–0.12 in. water).
  • When clogged, evaporative cooling pad replacement or cleaning is necessary in homes with such systems. There should be no dry spots and a consistent water flow across the pads. Because there is less resistance in dry places, air will flow through them preferentially.
  • Inspect and replace the water filters as needed. Fresh drinking water cannot enter the house through a clogged water filter. To increase interior ventilation, frequently remove dust and If practical get rid of the manure from the house before the hot season. Manure decomposition generates heat that adds to the home’s thermal load. The airflow in shallow pit houses and under cage batteries is impeded when there is an abundance of manure present.
  • In regions where the temperature is high, environmentally controlled homes and curtain-sided homes with tunnel ventilation are excellent. Fogging systems and stir fans should be used at open houses.
  • Insulated roofs lessen the amount of solar heat that enters the building through the roof and radiates inside.
  •    Make sure the water system can handle the extra water needs for birds as well as for foggers and evaporative cooling systems.
  • It is never appropriate to jeopardize a flock of stressed birds’ access to drinking water. Clear the area surrounding dwellings of any unnecessary metal objects, such as equipment, cars, nest boxes, and trash that could radiate heat into open spaces.
  • Preparing for times when the weather will be hot and taking the necessary management and dietary precautions before the temperature rises will help to minimize the impacts of heat stress.


  • The flock has a high demand for drinking water during hot weather conditions. At 21°C, the water-to-feed consumption ratio is typically 2:1; however, at 38°C, it rises to 8:1
  • Flocks under stress from the heat must have access to the necessary quantity of drinking water.
  • Make sure those who are drinking have access to enough water (> 70 ml/minute/nipple drinker). Verify that there is enough room for drinkers and that they are operating as intended.
  • More drinkers can be provided to floor-reared flocks to deal with the increased water consumption,
  • Water that is cooler will aid in lowering the birds’ body temperature and lessening the effects of heat stress.
  • It has been demonstrated that cooling drinking water by flushing water lines in the afternoon increases feed consumption and maintains egg production in heat-stressed layers.
  • Water below 25°C will help maintain higher water intakes and consequently encourage higher feed intake.
  • Plastic water lines quickly acclimate to the surrounding temperature, making it challenging to cool water temperature below the air temperature, especially at the end of long water lines.
  • Water intake will be significantly impacted by temperatures exceeding 30°C and will have additional detrimental effect on feed consumption.
  • Utilize vitamin and electrolyte supplements in drinking water to make up for salt, bicarbonate, chloride, and potassium lost through urine loss. It is preferable to take electrolyte supplements before a sudden increase in outside temperature.
  • If exposed to direct sunshine, drinking water from rooftop water tanks may become heated.

These water tanks must be covered, insulated, and painted a bright color to prevent direct sunlight.


The key to reducing the impacts of heat stress is to anticipate periods of high environmental temperatures and put in place suitable management and dietary measures before they occur.

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