poultry farming during hot weather

Managing flocks during hot weather

Dr. Ghulam Abbas Hashmi PhD Poultry Science

MSc (Hons) Poultry ScienceMSc (Hons) Animal Breeding and Genetics

M Phil Islamic Studies

Animals are divided into two types (1) Cold-blooded (hetero-thermic). (2) Warm-blooded (homo-thermic). Animals having

ability to maintain a uniform internal body temperature.

Ability to maintain a uniform internal body temperature is called as homeostasis.

Chickens are homo-thermic animals, however, this mechanism is efficient only when ambient temperature is within certain limits, they can not adjust well to extremes.

Chicken are also endothermicGeneral features of thermoregulation are similar to

that of other animalBirds use;Plumage, fat insulation , salt glands (Abbas et al., 2016)

Mechanism of heat production in birds(Glycolysis, Kreb’s cycle, pentose shunt)Factors which affect the heat productionEnzymes, vit. Hormones, physical activities, O2

consumed, ambient temp. and circadian rhythmMeasuring the heat productionBMRHeat balanceHeat lost from the body must equal the heat produced,

or there must be heat balance. Hm= conv + K + R +SHeat transfer (Cellular exchange, vascular exchange)

Heat Loss or GainHeat production in chickens body is through

metabolic processes & muscular activity.If the amount of heat produced by a bird is greater that

the amount it loses, the bird’s body temperature will increase.

Principles of Heat TransferSensible heat lossHeat that can be felt by the body. Also the heat or

energy that accompanies an actual change in temperature.

1) ConductionLoss of heat by contact of birds’ surface with the colder

surface of any surrounding object (floor, litter, slats, side walls, cage wires).

Contact area small, minute heat loss through conduction . It travel through one molecule to anotherThe rate of transfer depends upon thickness of

superimpose tissues.

2) ConvectionCool air comes in contact with birds’ surface air is

warmed. Heated air expands, rises & heat is carried away as warmer air moves away from the bird creating a wind chill effect.

10-25% loss by convectionAs the ambient temperature rises heat loss by convection

decreases and when it reaches body temperature there is little loss by this method.

In still air there is none.By increasing speed of air from inlets or with tunnel

ventilation, amount of heat lost from birds’ body through convection is increased.

(Abbas et al., 2016)

3. RadiationWhen temp. of birds surfaces is greater than surrounding

surface, heat is lost from birds’ body by electromagnetic radiation through the air to a distant object.

4) Fecal heat loss.5) Heat loss through egg production6) Evaporative Heat Loss/ Panting/ Latent Heat LossIn mammals, sweat glands present, body heat is moisture laden,

evaporation produces greater heat loss

Chiken lack sweat glandsThe chicken uses a process of evaporative cooling by

the vaporization of moisture from the damp lining of respiratory tract (lungs & air sacs).

Major heat loss from the body of birds when ambient temperature is high.

Body Temperature ControlInternal body temperature of birds is more variable than

mammals. Therefore no absolute body temperature in birds.

Adult chicken, 105 -107 0F(40.6-41.7 0C).Variations within & outside of this temperature range may be

due to.Body temp. newly hatched chicks 39.7 0C(103.5 0F), it daily

increases until a stable level at about 3 weeks.

Small breeds, higher body temperature than larger breeds.Older, heavier birds are less able to manage heat stress. Males slightly higher body temperature than females ( higher

metabolic rate & larger muscle mass in males).Activity related to body temperature.Molting birds, higher body temperature than fully feathered

birds.Broody hens, higher body temperature.During feeding & digestion of feed body temperature

increase.More light environment also increase body temperature.

For chicken there is range of environmental temperature to which body temperature remain essentially constant. This range depends upon: body weight, amount of plumage, amount, shape and distribution of feathers in body, acclimation, acclimatization and dehydration status of the body

chickens be housed & managed to provide an environment that will enable them to maintain thermal balance ( thermo neutral zone)

Thermo neutral Zone 25-37 0C (65-75 0F).

Core body temperature increases when ambient temperature goes above or below thermo neutral zone

Over the high critical ambient temp. body temp. increase which increase chemical reactions in the body thus more O2 is consumed.

Environment cannot accept this heat as ambient temperature is high.

When heat produced by birds is greater than that being lost, deep (core) body temperature will rise.

When it reaches a critical point, birds will die from heat prostration. This is called upper lethal temperature (116.8 0F, 47 0C).

On the other hands when temp. goes below 16 °C, the heat prod. Inside body increasesfirst by physical means (shivering, hurdling, fat/plumage insulation)

Then thyroid gland is activated and energy production increased till body CH2O and fat completely utilized. The lowering of the body temp. starts following the body temperature below physiological zero then the death of birds will occur.

Heat stressBirds are ‘heat stressed’ if they have difficulty

achieving a balance between body heat production and body heat loss. (Abbas et al., 2016)

This can occur at all ages and in all types of poultry. the body temperature of the broiler must remain very close to 41 C (106°F) body temperature rises more than 4 C above this, the bird will die.

Heat stressAdversely affects performance of birdsIncrease respiration rateCauses higher losses of CO2Increase blood pHDisrupt acid base balance (Abbas et al., 2016)

Heat stress and egg qualitythinner, weaker eggshells due to disruption of acid base balance

Another contributing factor to thin eggshells is reduced intake of calcium as feed consumption drops, and an increased loss of phosphorus

Decline productionreduced body weightPoor quality eggsIncreased respiration (more than 10 times)wings spreading Wet droppings Increased water consumptionAscites incidence increases Increased mortality


Carcass down grades. Stupor, staggers and terminal convulsions. rough skin. Lethargic birds. Increased cannibalism Tibial dyschondroplasia

Physiological effects

pH of blood plasma rises pH within the cells falls Urine output increases and so does electrolytes Bicarbonate (HCO3) is lost Stress hormones appear in the blood Gene function is disturbed Resources being diverted to homeostasis rather than

productionHeat shock proteins are activatedDiseases

Manipulations to combat heat stress

Managemetal Practices

Restricted feeding

Intermittent feeding

Feeding during cool hours of the day

Controlled environmental conditions

How to manage heat stressInsulation The heat is radiated from the ceiling into the house

(60%) .The design of the building and its ventilation system, the siting of new buildings and construction materials, will all have an effect. Roof colour, reflectivity, pitch and orientation, and whether the building is in the shade or not, are also factors which will have a small bearing on solar heat gain.

Roof reflectivity can be increased by cleaning and painting the surface with metallic zinc paint or by installing an aluminum roof

House design and location

VentilationHigh air speed is essential in heat stress relief. In

systems with lower stocking rates, the effects are greater.

Ensure that air passing over the birds from the inlets is as near to outside temperature and humidity as possible.

Remove the boundary layer of hot air around the birds, aiding convectional heat loss.

This is vital when birds are at, or near, peak stocking rate

Remove humid air from around the birds’ heads, making panting more efficient.

Makes the most of evaporative heat loss when, at very high temperatures (> 32 C),

All meat producers should aim for between 1 m/s and 3 m/s for relief against extreme heat.

To achieve 1.5 – 3 m/s, the house would usually need to be operInternal recirculation fans ating in a tunnel ventilation format.

can play an important role where air speeds over birds are poor.

In extremes of very high temperatures and very high humidities, cooling systems might be ineffective or detrimental.

There is about a 4.5% RH increase for every 1 C of cooling. A water supply that reduces temperature by 6 C must increase % RH by about 27%.

Managers should be aware that it is common for the house humidity probe not to accurately reflect this dramatic humidity increase.

The ventilation system should be checked to insure efficient operation prior to the arrival of the hot season.

any management technique which promotes feed consumption or increased activity during the peak hot periods may be counter productive.

The extra feed consumed will increase the bird’s heat load and probably result in additional mortality.

Fasting the broiler prior to or during peak hot periods of the day lessens the heat load and enhances survival.

The advantages are reduced metabolic heat output, and where feeds systems can be lifted, increased floor space and improved air distribution over the floor.

Fasting reduces the heat production from digestion, absorption and metabolism of nutrients.

Fasting also has a calming effect. Movement in animals occurs through muscle contraction which generates heat. In hot environments this heat production only adds to the heat load. Therefore, to lessen the heat load, broilers should be kept as calm as possible.

This is especially important during the hottest parts of the day. Once the hottest periods are over and ambient temperature starts to fall, the broilers will usually begin consuming feed again.

Where possible, reduce stocking densities during hot weather both in the shed and during transport.

Regularly maintain and test alarms and emergency ventilation equipment.

Make contingency plans in advance so all know their respective roles and ensure that someone is available with authority to take actions.

Reduce the thickness of litter. Don’t disturb the birds (excessive activity)during periods of

peak heat Drinkers should have sufficient water flow (> 70

ml/minute/nipple drinker Keeping water below 25°C add ice to water or flushing water

lines during the afternoon discontinue chlorination on extremely hot days or use H2O2

Management practices that require bird handling, such as beak trimming, transfer and vaccinations should be done in the early morning hours.

Using roof sprinklers during times of extremely high temperature can remove heat from the roof and cool the inside of the house.

feeding during the cool hours of the day Adjust fan thermostats so all fans run continuously during

the night and early morning hours. The goal is to maximize nighttime cooling in the house to prolong the period of moderate temperatures the next morning

Adjust the lighting program to provide more morning light hours (and fewer afternoon light hours) to encourage feed consumption during the cooler period of the day.

Avoid to use anticoccidial drugs during heat stress.Thermostats should be checked for accuracy. An

efficient stand-by generator must in working in case of a power outage during summer.

Early heat conditioning (EHC) seems to be one of the promising methods in enhancing heat resistance of broiler chickens.

Nutritional manipulations to combat heat stress

Reduction of protein concentration in rations

Increase of energy in rations

Supplementation of amino acids

Use of fats in rations

Reducing fiber contents of the diet

Supplementation of vitamins (especially vit. C, E)

Supplementation of sodium bicarbonate in rations


the inclusion of oil increased feed intake by 17.2% at 31°C compared to only 4.5% at temperatures of 10-18°C.Digestion of fat produces less heat than the digestion of carbohydrates and proteins.

Fat has also been shown to slow down feed passage through the gastro-intestinal tract, and therefore increases nutrient utilization. Up to 5% oil can be used. An additional advantage of oil is the content of linoleic acid, which improves the production and weight of the eggs.

Replace DL methionine with methionine hydroxyl analogue and betaine.

Increase the calcium content of the diet from 4 percent to 5 percent.

Replace 40-50 percent of any salt in the diet with sodium bicarbonate to help maintain egg shell quality.

Supplementation with additives such as synbiotics, phytobiotics, acidifiers and dextrose can also help in alleviating the heat stress.

Metabolism of excess protein is particularly heat-loading on the bird and exacerbates the ionic misbalance.

Formulate to digestible amino acid targets and do not apply a high crude protein minimum in the formula

The phosphorous requirement increases during heat stress. Increases of up to 5% should be appropriate under heat stress conditions.

Increase the digestible lysine to energy ratio with 5 to 10 % during heat-stress.

increased vitamin and mineral premixes by 25 %.

Imbalances in acid-base balance occur in heat stressed birds. Therefore, inclusion of various compounds in the diet or water is a common practice to alleviate the adverse effects of heat stress.

DEB should not be less than 250 mEq/kg to compensate electrolyte loss in heat stress (Ahmad and Sarwar, 2006)

supplemental salts such as protassium bicarbonate, potassium chloride, sodium chloride and ammonium chloride to the increased water consumption which results, not to the salts .Sodium zeolite and aspirin are also found to be beneficial

The addition of vitamin C @ 1g/kg to drinking water or feed helps to reduce corticosterone levels during heat stress.

Sodium bicarbonate (Baking soda)Sodium bicarbonate is a privileged compound and is being used in broiler feed industry, during summer.

Salient featuresSource of CO2

An antacidBuffering agentProducer of sodium carbonateSodium is equally available to that in NaCl for poultry


Dietary inclusion of Sodium bicarbonate @ 1%,

in layer diets during summer, is recommended

to improve the efficiency of egg production,

immune response against Newcastle disease and

digestibility of nutrients, in the birds.
