Discussion created on 10/29/2010

protect broilers from high temperature

Forum: How to protect broilers from high temperature?

Middle East has experienced an excessive temperature this summer and this affected the poultry industry and caused giant losses in farms and hen houses. In our region, as a general rule, the area fro rearing is 10 birds/m2 for broilers, 8 birds/m2, and 5 birds/m2 for broiler breeders.
The natural summer temperature in our country is 29-33°C. We can control it with ventilation and cooling but this case is out of control.

The results were:

In Broilers: Mortality is 30-50 and decreasing in the weight gain about 10 the price of 1kg was 1.78 $ after increasing of temperature the price of 1kg is 2.28$.
In Egg Layers: Mortality is 15-20 and decline in egg production by 20.
In Broiler Breeders: Mortality is 10 and decline in egg production and hatchability.

The intervention strategies:

1- Change the feed texture to compensate the depletion of energy and other feed ingredients.
2- Change the ventilation system in the hen house.
3- Used of antipyretic (such as aspirin) to decrease internal bodys temperature.
4- Choose the convenient vaccination applied time (at cooler time in day such as early morning).
5- Decreasing the density of population in the farm.
6- The cleanness of the air in the hen house (the birds cooling themselves by evaporation and they use their trachea to do it -all we know the birds had not any sweat glands- and if the air is contaminated with rious organisms such as E.coli the birds would be infected).


Waseem Alshible
Veterinary Doctor
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November 2, 2010

Changing feed texture compensate the depletion of energy and other feed ingredients that it decreased ingredient segregation, less time and energy expended for prehension, destruction of pathogenic organisms, thermal modification of starch and protein and improved palatability.

Arshaq Ramzee Arshaq Ramzee
Doctor of Veterinary Medicine
November 3, 2010
Best way to control excessive heat is to cool down the environment of the house, it is easy if house is environmentally controlled and relative humidity is low but in open houses and high humidity, the only possible measure is air movement in the house, must use fans to move the air fast enough to carry some humidity out of the house. Even in moving breeze, birds feel comfortable. If relative humidity is not high then temperature can be reduced by spray water in fine mist through fog producing pumps.

Another logical management tool is to manage the litter properly, other measure should be to increase levels of electrolytes in diet.
Nadir Alloui Nadir Alloui
Veterinary Doctor
November 4, 2010
In the future, we must use animals acclimated. Here is an experiment performed by Algerian researchers.

The purpose of this trial is to assess the impact of early acclimatization technique (exposure of chicks to the 5th day of age at an ambient temperature of 38 ° C for 24 hours) on the growth and subsequent thermo tolerance chicken subjected to the stresses of summer temperature in Algeria.

In our experimental conditions, establishment of chicks on the 5th day of age did not affect feed intake but has increased significantly overall weight gain between day 1 and day 49 compared with controls unacclimated (+5 %, P 0.05). This treatment also improved feed efficiency (P 0.05). This reflects improved digestibility reflected particularly by heights and volumes of intestinal villi greater.

Mortality from chronic exposure to heat has not been reduced by the treatment of early acclimatization (5% on average). However, in a second heat stress applied to the 50th day of age (35 ° C for 6 hours), a decrease in mortality of about 85% was recorded in chickens acclimated compared with controls. This improved thermo tolerance, especially in males was due to a decrease in body temperature recorded during the heat shock (-0.32 ° C in males).

After slaughter, carcasses ready to cook acclimated animals were heavier than those of controls, with a similar proportion of abdominal fat. This suggests greater muscle protein deposition promoted by the treatment of acclimatization. Metabolic and cellular mechanisms induced by the early acclimatization in chicken meat at high heat, remain unclear.

Sorry for my English
Dr Jaydip Mulik Dr Jaydip Mulik
Master Of Veterinary Science & Master of Business Administration
November 10, 2010
Dear Sir,
I would like to know if the mortality figures are in %

(In Broilers: Mortality is 30-50 and decreasing in the weight gain about 10 the price of 1kg was 1.78 $. After the increase in temperature, the price of 1kg is 2.28$.
In Egg Layers: Mortality is 15-20 and decline in egg production by 20.
In Broiler Breeders: Mortality is 10 and decline in egg production and hatchability)

To control the birds from heat stroke whatever Managemental tips you have suggested are useful to check the mortality up to some extent but apart from that if you provide the supplementary nutrients viz.Vit C, electrolytes etc then the birds will recover faster from heat stress.

Thanks & regards,

Dr Jaydip
Hafiz Imran Shakoor Hafiz Imran Shakoor
Animal Nutritionist
November 24, 2010
Heat stress management is complicated phenomenon. Its management require modification at every steps from breeder farm to broiler farm.

Selection and development of heat resistant strains. It is topic of interests among geneticists.
Selection of strains with less feathering to facilitate heat loss.
Incubating eggs at higher temperature for specific time to enable the chicks to bear heat shocks, avoid chicks to be dehydrated
Brooding chicks at higher temperature to accalamitize the birds with high ambient temperatures.
Using forced ventilation system to cool the birds instead letting the birds cool their body through evaporative cooling which is the last option that the bird utilize to cool their bodies.
Water management is very important because cool drinking water helps to lower body temperature. Water being a good conductor carries heat from deeper body parts to the surface.
Use of electrolytes like Na, K, Cl, HCO3 because their excretion increase during heat stress. Their supply not only maintain electrolyte balance but also increase water intake.
Use of anti heat stress vitamins and minerals like vitamin C, Zn, Cr.
Feeding during cool hours to avoid metabolic heat production during stress hours.
Dr. Rahul Hardas Dr. Rahul Hardas
Veterinary Doctor
March 9, 2011
Use of tranquilizer in broiler can to prevent the bird in heating condition also use of Potassium chloride in a day water as in heat the bird are Potassium ion defeiceincy as they become extracellular due to panting leading to also help to maintain adequate water supply.
Adding more calcium diet in layers as increased respiration rate alters the acid-base balance because carbon dioxide bird concentration in the blood increases resulting higher blood PH levels lead to thin shelled egg formation.
Birds are prone to infectious disease on account of low resistance from heat However addition of Vitamin E in diet has shown beneficial effect on layers and Broilers
May 6, 2011
There are 3 ways heat to loose, 1. Conduction, 2. Convection & 3. radiation. All these measures should be taken care to lose heat from body. Another important thing is to make avaiable Cool, Fresh sanitized water for birds to drink, soda bi carb m/b used to control blood PH. In Feed, energy m/b increased to compansate quantity, additional minerals & vitamines be added upto 5-10%. Do not withdraw or strave birds which create additional stress on birds. As the enviromental temperature is high, birds them selves do not take feed. This is practically experienced by me. whenever bird feel comfortable, may go to feeder & take little quantity & drink plenty of water which is good. Starving & feed holding induce stress on birds and after feeding in cool hours or any time, all rush to feeders as are hungry. Feed more hurridely more quantum & huddling cause transfer of heat from 1 to other birds by contact & increase body temp again, along with feed digestion , start Heat generation in body. So this should be avoided. Vit C, minerals in water may help to reduce stress. Just need to keep Basic at Proper.
hector del rosario hector del rosario
Veterinary Doctor
May 11, 2011
Feeding of broilers in hot climate needs carefull considerations, some broiler farmer are witholding the feeds during the hottest part of the day and then resuming it when the temperature starts to go down, For me It is more stressfull for the broilers and agravating further the effect of heat stress, when they starts resuming the feeding again , broiler tends to rush to the feeder to take their feeds and during this period, competitions and boxing out in order for them to get to the feed first give them more stress and eventually further enhancing the effect of heat stress, Almost all the breeds of broiler are designed to become borasious eater to make them grow faster, My obserbations are, The more the availability of the feeds during the hottest part of the day the more convenient for the chickens, 1. chickens dont rush to the feeder because they know there are lots of feeds for them to consume leaving them competition and boxing out free, 2. chickens dont store much feed into their crops because feeds are available at all times, unlike when restricted feeding is practice, they tend to store feeds to tneir crops making them prone to crop impaction and eventually heat stroke. 3 broilers control themselves their feeding habbit, even there are lots of feeds arround them during hot period, they dont take much feed, intead they give way to panting wich help them reduce body heat, 4 Not all chickens in one pen go hungry at the same time, so the availability of feeds during hot weather is important to maintain a stress free flock, Giving enough feeds availability during hot weather plus good ventilation and steady supply of clean drinking water plus a clean environment for the chicken can help in the battle of heat stress
Dr Jaydip Mulik Dr Jaydip Mulik
Master Of Veterinary Science & Master of Business Administration
May 11, 2011
Dear All,

I wish to add some following points thoroughly to overcome the problem of heat stress :

Heat Stress & Ambient Temperature
55° to 75°F
Thermal neutral zone. The temperature range in which the bird does not need to alter its basic metabolic rate or behavior to maintain its body temperature.
65° to 75°F
Ideal temperature range.
75° to 85°F
A slight reduction in feed consumption can be expected, but if nutrient intake is adequate, production efficiency is good. Egg size may be reduced and shell quality may suffer as temperatures reach the top of this range.
85° to 90°F
Feed consumption falls further. Weight gains are lower. Egg size and shell quality deteriorate. Egg production usually suffers. Cooling procedures should be started before this temperature range is reached.
90° to 95°F
Feed consumption continues to drop. There is some danger of heat prostration among layers, especially the heavier birds and those in full production. At these temperatures, cooling procedures must be carried out.
95° to 100°F
Heat prostration is probable. Emergency measures may be needed. Egg production and feed consumption are severely reduced. Water consumption is very high.
Over 100°F
Emergency measures are needed to cool birds. Survival is the concern at these temperatures
Methods of Heat Loss
During the summer months, when daily temperatures regularly reach the mid- to upper 90s, it becomes critical for the birds to dissipate body heat to the surrounding environment. Poultry do not sweat and therefore must dissipate heat in other ways to maintain their body temperature at approximately 105oF. Body heat is dissipated to the surrounding environment through radiation, conduction, convection, and evaporation . The first three avenues are known as sensible heat loss; these methods are effective when the environmental temperature is below or within the thermal neutral zone of the bird (55o to 75°F) The proportion of heat lost through radiation, conduction, and convection depends upon the temperature difference between the bird and its environment. The bird loses heat from surfaces such as wattles, shanks, and unfeathered areas under wings. To maintain body temperature by sensible heat loss, the bird does not need to drastically alter its normal behavioral patterns, feed intake, or metabolism. The purpose of poultry house ventilation is to maintain a high enough air velocity or a low enough temperature in the house that the birds can maintain body temperature by sensible heat loss.
Sensible Heat Loss Methods
Radiation –
Flow of thermal energy without the aid of a material medium between two surfaces All surfaces radiate heat and receive radiation back; the net radiation heat flow is from higher to lower temperature surfaces.
Conduction –
Thermal energy flow through a medium or between objects in physical contact. Direction of energy transfer depends on a temperature gradient; heat moves from areas of higher to lower temperature.
Convection –
Heat flow through a fluid medium such as air; thermal energy moves by conduction between a solid surface and the layer of air next to the surface, and the thermal energy is carried away by the flow of air over the surface. Energy transfer to the air depends on temperature and movement of air across the skin surface; heat is transferred to air moving across the skin surface if the air is at a lower temperature than the skin.
Latent Heat Loss Method

Evaporation –
The transfer of heat when a liquid is converted to a gas; when water is converted from a liquid to a vapor, heat is utilized. Energy transfer is influenced by the relative humidity, temperature, and air movement; heat is transferred from the animal's body to water, turning it to water vapor.

Once the environmental temperature reaches approximately 77°F, the method of heat loss begins shifting from sensible to evaporative heat loss. Dissipation of body heat by the evaporative process requires the bird to expend energy by panting (hyperventilation), which begins to occur at about 80°F.
Physiological Effects of Panting
Panting removes heat by the evaporation of water from the moist lining of the respiratory tract. However, panting itself generates body heat, and it causes poultry to eliminate water from the body. It can induce respiratory alkalosis, which occurs because the bird "blows off" excessive carbon dioxide (CO2) when it pants. As a result, body fluids become more alkaline, causing the kidneys to excrete excessive amounts of several electrolytes. As the shift in body fluid pH occurs, feed intake is increasingly depressed, adversely affecting growth, production, and overall performance of the bird. During the hot summer months, evaporative heat loss typically becomes the primary method by which birds regulate their body temperature unless proper ventilation is provided and other steps are taken to reduce heat stress.
Feed and Feeder Management

Any management technique that increases nutrient intake during heat stress will minimize the drop in production efficiency. Three easy ways to increase nutrient consumption are to increase nutrient density, take advantage of natural increases in feed consumption at certain times of the day, and adjust ventilation fans to provide more cooling during the evening. A very direct way to ensure optimum nutrient intake despite decreases in feed consumption is to increase the nutrient density of the ration. Recent research indicates that low phosphorus consumption can contribute to increased heat prostration losses. A second alternative is to feed the birds at the time of day when feed consumption is highest. The light-to-dark cycle results in a U-shaped feed consumption curve. Shortly after light come on, feed consumption is high. It gradually declines during midday and then increases about 1 hour before lights are turned off. If birds are fed during the cool part of the day, feed consumption will be higher. Birds should not be fed during the afternoon in periods of hot weather since this will increase the amount of body heat that they must dissipate and thus increase the potential for heat prostration. Abrupt changes in feeding times should be avoided. A third technique is to cool the birds as much as possible during the evening hours. Hens or meat birds tend to build up body heat during extended periods of hot weather. If their body temperature can be reduced during the evening , the birds will be able to consume more feed in the early morning. The house can bee cooled in the evening by setting the fan thermostats so that the fans will continue to run until the internal house temperature reaches 75°F (65°F for mature birds).
Under hot and humid conditions, feed should not be stored for longer than a week.

The bird's body temperature increases after feed ingestion due to the thermogenic processes of digestion and metabolism. With morning feeding, the thermogenic effect coincides with the rising environmental
temperature, aggravating heat stress, The thermogenic effect lasts for 8-10 hours at 35°C, compared to just 2 hours at /20°C./ Metabolic heat production is 20-70% less in starved birds than in fed birds. Therefore,
during hot weather, birds should be deprived of feed while the temperature is reaching and at its peak. Feeding during early and late hours of the day will help to minimize growth checks and mortality in broilers. Intermittent feeding, i.e. providing the light for 30 minutes followed by 3 hours dark, may also reduce the activity (heat production) of the bird but 20-30% more feeder and waterier space will be required.

For layers, feeding during later part of the day will ensure sufficient calcium is available for optimum shell calcification, Low feed intake is the main cause of poor performance at high temperatures. The following practices can help to raise feed consumption and may be worthwhile considering:

Wet mash feeding

pellet or crumble form of feed

Low-calcium diets with choice feeding of calcium sources

Frequent feeding and stirring of feed in the feeder

Addition of fat or molasses so to increase feed palatability.
Layers will produce eggs constantly in the temperature range of 10-30°C. Above 30°C, performance will be depressed in terms of growth, feed intake, egg production, egg size and eggshell quality. Nutritional imbalances can also result from poor quality control and lack of regulations for feeds, feed ingredients and feed additives.
Furthermore, mycotoxins develop very quickly in hot and humid conditions, leading to loss of production, immunosuppression and higher mortality. Routine management practices, e.g. medication, vaccination,
beak trimming etc, also add to the stress.


Energy intake is the most important nutrient limiting bird performance at high temperatures. The energy requirement for maintenance decreases by about 30kcal/day with increase in environmental temperature above 21
°C. Although the energy requirement for maintenance is lower at higher temperatures, most of the energy is wasted in heat dissipation so the absolute energy requirement is not affected by heat stress. The feed energy concentration should be adjusted to allow for the reduction in feed intake at higher temperatures. Feed intake changes
about 1.72% for every 1°C variation in ambient temperature between 18 and 32°C. However, the decline is much faster (5% for each 1°C) when the temperature rises to 32-38°C. Measures to increase feed intake include
the inclusion of fat in the diet. Feed consumption increased up to 17% by 5% fat supplementation in heat stressed birds because fat improves palatability. In addition, fat offers an extra calorific value by decreasing the rate of passage of digest a, thereby increasing the utilization of nutrients.

Fats or oils with more saturated fatty acids are preferred in hot humid climates. The concentration of energy should be increased by 10% during heat stress, whilst the concentration of other nutrients should be increased by 25%.


The requirements for protein and amino acids are independent of environmental temperature so heat stress does not affect bird performance as long as the protein requirement is met. However, heat stress reduces feed intake and the levels of protein/amino acids need to be increased with the environmental temperature up to 30°C. At even higher temperatures, heat stress has a direct effect on production and there is no benefit in raising the protein level.

The correct amino acid balance in the diet minimizes fat deposition in the liver, thereby increasing the survival of birds under heat stress. So, a low protein diet with balanced critical amino acids (methionine and lysine) is more beneficial than a diet high in total protein during hot periods. The oxidation of excess protein or amino acids generates metabolic heat.


Heat stress reduces calcium intake and the conversion of vitamin D3 to its metabolically active form, ,25(OH)2D3, which is essential for the absorption and utilization of calcium. In effect, the calcium
requirement of layers, particularly older birds, is increased at high environmental temperatures. To overcome this effect, extra calcium should be provided at the rate of I g/bird in the summer months in the form of oyster shell grit or limestone. Supplementation should be made over the normal dietary calcium level (3.75g/bird/d) recommended for layers.

However, excessive levels of calcium reduce feed intake due to the physiological limit of calcium appetite and also reduced palatability Instead of increasing the diet specification, the calcium should be offered separately as a choice feed. Better results are obtained by offering the calcium source in the afternoon. The optimum particle size is the one that supplies the required calcium at me time of shell formation. The minimum size to improve gizzard retention is about 1mm.The phosphorus level in diet must not be forgotten as excessive
phosphorus inhibits the release of bone calcium and the formation of calcium carbonate in shell gland, thereby reducing the shell quality.

Supplementing the diet with 0.5% sodium bicarbonate or 0.3-1.0% ammonium chloride or sodium zeolites can alleviate the alkalosis caused by heat stress. Sodium bicarbonate stimulates feed and .water intake at high
environmental temperature. The body weight gain can be increased up to 9% by addition of these chemicals in the feed of heat-stressed broilers.

The excretion of potassium through urine is significantly higher at 35°C than at 24°C. The potassium requirement increases from 0.4-0.6% with a rise in temperature from 25 to 38°C. A daily potassium intake of
1.8-2.3g potassium is needed by each bird for maximum weight gain under hot conditions.

To compensate for the reduced feed intake under heat stress, dietary allowances for electrolytes (sodium, potassium and chloride) may be increased by 1.5% for each 1°C rise in temperature above 20°C.
Electrolytes are also present in the drinking water and these levels need to be taken into consideration. Excess intake of electrolytes can lead to wet droppings, Potassium chloride can be added to the drinking water (to give 0.24-0.30% K) but care must be taken to avoid imbalances. Excess chloride is known to decrease the blood bicarbonate concentration.

During heat stress, the bird tries to maintain its body temperature by increased respiration, i.e. evaporation of metabolic water, which may considerably increase the water requirement. The addition of electrolytes (and/or vitamin C) to cold water helps to increasing feed intake by heat stressed birds.

Additional allowances of ascorbic acid (vitamin C), vitamins A, E, and D3 and thiamine can improve bird performance at higher temperatures. However, the loss of vitamin activity either in premix or in feed during storage particularly at elevated environmental temperature is a prime concern and probably explains the conflicting results on the effects of vitamin supplementation during heat stress. High temperature, moisture, rancid fats, trace minerals and choline speed up the denaturation of vitamins. Vitamin activity in feeds can be maintained by using feed antioxidants, gelatin encapsulated vitamins, appropriate storing conditions and adding choline and trace minerals separately from other

Ascorbic acid synthesis is decreased at elevated environmental temperature, making it an essential dietary supplement during the summer. The vitamin helps to control the increase in body temperature and plasma corticosterone concentration. It also improves eggshell quality via its role in the formation of the shell's organic matrix. Furthermore, it protects the immune system and reduces mortality in growing birds infected with IBD in a hot environment by protecting the lymphoid organs and thyroid activity. Supplementation of ascorbic acid (200-600mg/kg diet) improves growth, egg production, number of hatching eggs, feed efficiency, egg weight, shell quality and livability during heat stress.

The absorption of vitamin A declines at high temperatures. In broiler breeders, a three fold increase in supplementation has been found to be beneficial.

Vitamin E protects the cell membrane and boosts the immune system so additional dietary supplementation may be advantageous during hot weather. Mortality due to E. coli infection reduced significantly by supplementation of vitamin E in diet.

Heat stress is known to interfere with the conversion of vitamin D3 to its metabolically active form, i.e. 1,25(OH)2D3, so higher dietary levels maybe justified during periods of high temperature. The active form of vitamin D3 is involved in the synthesis of calcium binding protein, essential for calcium and phosphorus homeostasis.
A number of compounds are effective in reducing the ill effects associated with hyperthermia although their cost may be prohibitive.Antipyretic compounds, e.g. salicylic acid and aspirin, minimize the levels of catecholamine in the blood during heat stress.

The performance of heat stressed birds can be increased with magnesium aspartate, zinc Sulphate, diazepam, metyrapone or clonidine in the feed. Aureomycin has been found lo alleviate the stress (growth depression) caused by injection of foreign protein or salmonella end toxin but it has not always been found to be beneficial.

Acetylsalicylic acid (3% of the diet) increased me weight gain and shell quality in some reports but the
effects are inconsistent. Resin pine, an alkaloid from the Rawolfia plant is known to prevent the loss of carbon dioxide from birds subjected to high environmental temperature, thus stabilizing the blood acid base balance.

Flunixin, an anti inflammatory analgesic drug at 0.28-2.2mg/kg bodyweight per day increased water consumption by 150-300ml/bird/day. The anticoccidial compound, nicarbazine (at the standard dose of 125mg/kg), has increased the mortality of broilers to up to 90% during heat stress.

Adding potassium chloride in drinking water can ameliorate the toxic effects.
Techniques for Managing Heat Stress

A grass cover on the grounds surrounding the poultry house will reduce the reflection of sunlight into the house. Vegetation should be kept trimmed to avoid blocking air movement and to help reduce rodent problems. Shade trees should be located where they do not restrict air movement. Fans should be routinely maintained. Maintenance should include cleaning the fan and keeping pulleys and belts in good condition and properly adjusted. Poultry netting on sidewalls or air inlets often will pick up enough dust to restrict air movement and should be cleaned regularly. Keeping a reliable, clean, cool source of water available to poultry is essential to help the birds cope with high temperatures. Because the birds excrete electrolytes during periods of heat stress, electrolytes can be added to the drinking water to replace those that are lost and to stimulate water consumption. Avoid placing water pipes near the ceiling where the water will gain extra heat. Line in which the water has become warm can be drained to allow cooler water to reach the waterers. A second well or access to an emergency source of water should be available in case the primary water source fails. Another factor that affects heat gain of a house is the condition of the roof. A shiny surface can reflect twice as much solar radiation as a rusty or dark metal roof. Roofs should be kept free of dust and rust. Roof reflectivity can be increased by cleaning and painting the surface with a metallic zinc paint or by installing an aluminum roof. These practices are particularly effective for buildings that are under insulated.
Equipment and Ventilation Techniques for Reducing Heat Stress

During the summer when the temperature and humidity are high, proper poultry house ventilation is vital to ensure the necessary removal of heat and the continued productivity of the flock. Poultry house ventilation systems have a number of components. These include curtains, fans, fogging nozzles, evaporative cooling pads, timers, static pressure controllers, and thermostats. Most ventilation systems can provide an adequate indoor environment when properly managed. If the design and management of the ventilation system fails to satisfy the flock's ventilation needs, stale, contaminated air can build up in the poultry house. Stale air and contaminants, including ammonia, moisture carbon dioxide, carbon monoxide, and dust, can cause stress and lead to depressed performance. Stress may impair the immune system and increase susceptibility to disease. To reduce problems with stale air and contaminants, air temperature, air speed, and relative humidity must be controlled by careful management of the ventilation system.

Natural Ventilation

Curtain-sided houses rely extensively on natural air movement. These houses work best when they are located away from obstructions such as other buildings or trees that can block natural air currents. To avoid total reliance on natural air movement, most producers have added circulation fans in curtain houses to increase air movement and promote the loss of body heat from the birds. These fans should be spaced and positioned to maintain air movement between fans and to direct their flow in a way that will increase the turbulent air movement around the birds. Spacing of the fans depends somewhat on their size, but they are generally spaced about 25 to 30 feet apart in curtain layer houses and 40 to 50 feet apart in broiler houses. Circulation fans should be controlled by thermostats set at about 85 o F (or lower in hot weather). To save energy, the fans should shut off when the temperature drops below 85 o F except during periods of extended hot weather. At those times, it is advantageous to leave the circulation fans running through the cool evening hours by turning the thermostats down to 75 o F or even lower. This practice will lower the inside temperature faster, providing the birds with a cooler environment in which to dissipate stored body heat.
Foggers reduce air temperature in the house on hot days (90 o to 95 o F) when humidity is low, especially during midday when humidity levels are lowest and temperature is highest. The foggers inject fine water particles into the warm inside air. As the water vaporizes, heat is absorbed from the air, lowering its effective temperature. When foggers are used, they should be operated intermittently or designed to avoid excessive water flow into the environment. If too much water flows through the foggers, humidity levels may increase to the point where birds can no longer cool themselves by evaporation. In addition, litter made wet by excessive fogging can lead to performance and health problems. The appropriate water flow rate and timer settings depend on the method of ventilation, ventilation rate, bird size, and outdoor conditions. Fogging systems in naturally ventilated house are typically designed for a water flow rate of 50 to 100 gallons per hour.

Forced Ventilation

In forced ventilation systems, all air movement is produced by fans in the building walls. Houses that use this type of ventilation are also referred to as controlled environment systems. Power ventilation houses can provide good, uniform airflow patterns under hot summer conditions if correct static pressure is maintained and airflow obstructions are avoided. It is very important to determine how much air should be moved through the building. This can be accomplished in two ways. Approximate values for the minimum volume of air required per pound of poultry body weight are given in Table 3. These values can be used to determine the total fan capacity required for the house. Keep in mind, however, that the rates shown are minimum estimates, and it is best to plan for the worst possible case. For example, the efficiency of fans is greatly reduced if they are allowed to become excessively dirty, reducing the airflow through the building.

Dr Jaydip
Ganesh Kumar Dahal Ganesh Kumar Dahal
Managing Director MDH Pharmaceuticals Pvt.Ltd.
May 11, 2011
All the points discussed in this forum to prevent heat stress by management practice and alteration in feed supplements will be very effective.

As we are aware that birds are prone to diseases due to low resistance power during heat stress and their complicated respiratory system also elevates problem during hot whether so good litter management would be an additional tool to reduce mortality.

Bird respiration system is complex. The inhaled air flows direct into air sacs. The air is then pushed back to wards head into area of lungs where exchange of oxygen and carbon dioxide takes place. The flow of air directly into air sacs helps the deposition of pollutants in the different regions of respiratory system. The lesions of ammonia are more pronounced in thoracic air sacs since contaminated air spends more time in thoracic sacs.

Poultry exposed to 20 ppm of ammonia are more sensitive to infection and vaccine failures.

A bird can not cough as it does not have a diaphragm like mammals. However, a bird has small hair like projection in the wind pipe called “Cilia” to help expel foreign material.

Exposure of chicken to dust & ammonia results in decilliation of the upper respiratory tract of birds causing colonization of E.coli & Mycoplasma leads to respiratory tract infections and spread of diseases in the farm.

Even inhalable air born dust concentration is about 2.0 mg/m3 in battery cage system. Where as in litter system, the dust contains varying concentration of stuff, litter particles, feather compounds, carrier gases, endo-toxins and large quantity of different micro organisms which could be floating in the air expedite pass on polluted air in respiratory system during panting of birds in hot whether.

Ammonia gas is lighter than air and is a corrosive alkaline gas. Ammonia gas is water soluble and can thus be easily absorbed in the dust particles floating in the air in the poultry house which may settle in as they are inhaled by birds in cages or birds on deep litter system.

The poultry litter has an average pH of 8.0 – 9.0, this is considered a high pH or alkaline. The pH can influence the ammonia volatilization. Ammonia release from litter is minimum when litter pH is below 7; emission exceeds when pH is 8 and above. At litter pH higher than 5.6, the economically devastating bacteria like E.coli, Salmonella, Clostridium, and Campylobacter do grow fast.

If we control litter ammonia & pathogenic microbes in hot season then we would be able to reduce mortality considerably.

A litter management product can solve the problem of ammonia as well as potentially pathogenic microbes of litter.
Stephen Adejoro Dr Stephen Adejoro Dr
Doctor of Veterinary Medicine
May 11, 2011
Nanotechnology can now provide answers to points raised by Ganesh in other to minimise vaccination failures reduce resistance development and improve litter quality
All this will help to minimise the effect of heat stress on birds,A company Olmix of France have developed a letest technology that ameliorates effect of heat stress abserved by Ganesh
Stephen Adejoro
Dr Muhammad Arshad Dr Muhammad Arshad
General Manager
May 16, 2011
. Some points to be considered during summer management are:
• Increase in the energy content of the feed is required to take care of the reduction in the feed intake in spite of the fact that in summer, the maintenance energy requirementfor the bird is comparativelyless. The increase inenergy is best achieved by adding fat (oil) that stimulatesfeed intake and further improves the palatability of feed. Fat also reduces the rate of passage of ingesta within the digestive system. (At the same time we need to reduce daily intake of energy by the bird)
• Proportional increase in other nutrients, proportionate to the increase in the energy level
• Minimising the excess of amino acids improves feed intake
• A diet with lower protein levels and supplemented with limiting amino acids will help in reducing stress to the kidney and also lowering of ammonia levels in poultry houses
• Ammonium chloride supplementation through feed improves weight gain.
• Sodium bicarbonate addition in diet is beneficial
• Micro minerals may be over the normal requirement
• Inclusion of potassium .5 kg / chloride 0.5 kg / MT feed in prestarter and starter diets is also useful
• Feed electrolyte balance should be maintained more than 250 mEq especially in the summer. (The bicarbonate ions c o m i n g f r o m s o d i u m bicarbonate should also be considered while balancing)
• Usage of Vitamin C (coated) at a minimum dose of 100g / MT of feed is advisable
• Chelated trace minerals usage is advisable
• Increase in the fibre content of the feed is useful in slowing down the intestinal motility (which is normally higher in the summer). Including at least 2- 3% SFDOC to increase the fibre in all types of feed will deliver better results. (This will contribute at least 0.3 to 0.4% increases in the fibre of the diet) Inclusion of enzymes is preferable during summer months Addition of Phytase (80 to 200 g/ton) depending on the feed formula is useful in reducing the stress to the birds
Dr. Ajeet Bishnoi Dr. Ajeet Bishnoi
Marketing Manager
May 25, 2011
Dear All
As the heat stress is a concern in most part of the world and creates huge losses in the productivity and health of the poultry birds.

One of the factor which alters in the summer stressed birds is a hormone named "CORTISOL" secreted from adrenal gland after stimulation of Hypothalamus due to heat and after crossing thermoneutral zone.

This particular hormone is very much responsible for production losses, mortality and immunosuppression. which in turn cause loss in the poultry farming during summers due to poor production , morbidity and mortality

Some plant based products proven very effective in these sort of stress management and immunomodulation. One of such products is STRESROAK which is very effective in summer stress management along with good management measures as discussed in the forum


Dr Ajeet Bishnoi
May 25, 2011
i think the points raised by dr ,jaydip mulik is exlpanatory to the issue,and taking his data into consideration and the suggestion is sufficient to overcome the problem.overall summer stress is unavoidable and birds do have the tendency to acclimitize the heat ,and there is no need to do research for heat acclimization as suggested by some experts. cool drinking water,ventilation appropriiate management and balanced diet all this is needed.
dr mulik i shall follow your suggestions in my units.thanks.

secondly i had a1.89 kg broiler with a ambient temp of 36.8Cand the birds were managed by -no feeding in afternoon hrs ,reducing the litter thickness and spraying a cool water jet on birds during early afternoon hrs help me to controll mortality and achieve target without any additional efforts. [personal exprience]
May 26, 2011
Heat strees during summer months which last more than 5 months have a negative effect on poultry industry in the middle east country .Most small farms does not work during summer months which increase the problem ( huge loss ) All effort which have been mentioned above can help but how much . We need to use a combination of all methods previously stated ( which will increase production cost ) Heat stress is a complex problem in the middle east and it can not be solved by single action , we need to use a combination of all methods mentioned above and use a circulating fans insid poultry house . Increasing oil or fat levels in the diet will help to reduce heat increment but these sourse of energy is expensive too .Thus from my experience it is better to use all methods togethor and dont forget water temp. it is very important.
Pro.Dr.Essa AL-Mashhadani
Safdar Javed Safdar Javed
Veterinary Doctor
July 10, 2012
Badr Alfadil Badr Alfadil
Veterinary Doctor
November 28, 2012

Is practical to add blocks of ice to the main water tank during the peak of hot hours ?

Surinder Khanna Surinder Khanna
May 28, 2019

I feel use of medicines have little role in reducing mortality or heat stress . maintaining deb level is more important than using additional electrolytes.

April 1, 2021
Farm ventilation design will play a huge role in alleviating the negative effects associated with heat stress.
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Fred Hoerr
Fred Hoerr
DVM, PhD, Diplomate ACVP, ACPV
  Nashville, Tennessee, United States
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