Understanding and managing heat stress in poultry

Understanding and managing heat stress in

poultry Dr/ Hesham kotb

Alwadi broiler breeder veterinary supervisor KSA

D.V.M D.P.H

What is heat stress?

O Birds are ‘heat stressed’ if they have

difficulty achieving a balance between body

heat production and body heat loss.

O This can occur at all ages and in all types of

poultry.

O he body temperature of the broiler must

remain very close to 41 C (106F) body

temperature rises more than 4 C above this,

the bird will die.

Diagram of Thermoneutral Zone

O in hot weather, damp litter will make heat

stressed birds feel much more

uncomfortable than dry litter.

O In dry litter, birds will attempt to dust

bathe more readily to aid cooling.

O Turkeys, broilers and layers perform well in

comfortable summer temperatures between 70–

80oF (21-27oC).

O When ambient (surrounding) temperatures rise

above 80oF, feed intake, growth and production are

affected.

O Heat exhaustion and death will occur when

temperatures exceed 90oF (32oC)

O High humidity and high ambient temperatures are

extremely stressful for birds.

O If the amount of heat produced by a bird is greater

that the amount it loses, the bird’s body

temperature will increase.

O During hot weather birds will limit their daytime

activity and will reduce feed consumption or stop

eating.

O Feed consumption and digestion increases body

temperature, and thus birds will decrease their

feed intake to reduce their body heat production.

O Decreased feed intake will affect bird performance

and profitability. Water consumption will also

increase in hot weather, which will result in wetter

droppings and litter.

O In order to keep cool, birds will increase their

respiration rate as much as ten times the normal

rate and indulge in throat flutters or panting.

O Throat fluttering allows the evaporation of heat

by moving air in and out of the throat area

without actually entering the lungs.

O This method is very efficient on hot dry days,

but it is not very helpful during hot humid

weather because evaporation is more difficult.

O Older, heavier birds are less able to manage heat stress.

O Due to the lower body surface area per kilogram of body weight, older birds produce more internal heat and are less able to cool down by convection and evaporation.

O Older birds have more feathering and hence more insulation, which also makes it more difficult to get rid of body heat. In addition, as birds become larger there is less space between individuals in the poultry

O house, which traps more heat between birds and significantly increases the temperature at the floor level.

O Thus, air movement is an important method of keeping older flocks cool.

EFFECT OF HEAT STRESS

THE EFFECT OF HEAT STRESS ON EGG SHELL QUALITY

O Heat-stressed laying flocks often lay eggs with thinner, weaker

eggshells because of an acid/base disturbance occurring in the

blood as a result of panting (hyperventilation, Agular reflex).

O As birds hyperventilate to lose body heat, there is excessive loss of

CO2 gas from their lungs and blood. Lower CO2 in blood causes

blood pH to elevate or become more alkaline.

O This condition is called respiratory alkalosis. The higher blood pH

reduces the activity of the enzyme carbonic anhydrase, resulting in

reduced calcium and carbonate ions transferred from blood to the

shell gland (uterus).

O Increasing the amount of calcium in the diet will not correct this

problem. Another contributing factor to thin eggshells is reduced

intake of calcium as feed consumption drops, and an increased

loss of phosphorus

Signs of heat stress

Visible signs of heat stress in poultry

O In general, birds will be suffering heat stress when any

of the following signs are evident:

O Gasping, panting, panting respiration - up to 250

breaths per minute - mediating evaporative cooling from

the surface of the lungs (80% of heat is lost this way)

O wings spreading

O Stupor, staggers and terminal convulsions.

O Slowness and lethargy.

O Increased cannibalism

O More Carcass down grades.

O Light body weight, poor colouring and

rough skin.

O Egg production drop for no apparent

reason

O Reduced egg size, poorer egg shell

quality

O Increased mortality

O Increased output of urine - further loss of

electrolytes

O Wet droppings develop

O Thirst increases- many times

O Bone metabolism is disturbed e.g. tibial

dyschondroplasia

O Ascites incidence increases

Invisible signs of heat stress in poultry

O pH of blood plasma rises

O pH within the cells falls

O Urine output increases and so does

electrolytes

O Bicarbonate (HCO3) is lost

O Stress hormones appear in the blood

O Gene function is disturbed

O Resources being diverted to unproductive

efforts by the animal (bird) to restore balance

(homeostasis)

O Heat shock proteins are activated to shut down

metabolic reactions and to protect heat-

sensitive tissues.

O Responses to intercurrent diseases or

pathogens decline rapidly.

O All production is stopped due to loss of

homeostasis

PM Picture O Congestion and build up of fluids and blood is common.

Lesions are often present.

O Color changes to a pale yellow and is congested

O Kidney : Swells and is inflamed, water blood and urine

accumulates.

O Muscles are dry and sticky to touch.

O Blood is thicker and darker than normal.

O Crop and gizzard are empty and dry.

O Gizzard lining peels off easily

Physiological heat stress adaptation

O Flocks not previously acclimated to high temperatures typically suffer the greatest loss

O Young birds exposed to high environmental temperatures are more thermo tolerant later in life, due to the production of heat shock proteins.

O The best method of cooling during periods of lower humidity is evaporative cooling (fogger, mister or cool pad).

How do birds respond to increasing temperature?

O Birds will try to re-establish their heat

balance with the surrounding by changing

their normal behaviour. Birds may:

O ● Try to move away from other birds.

O ● Move against cooler surfaces, such as the

block walls or into moving air streams.

O ● Lift their wings away from their bodies to

reduce insulation and expose any areas of

skin that have no feathers.

O ● Elect to pant slowly.

O ● Rest to reduce heat generated by activity.

O ● Reduce feed intake.

O ● Increase water consumption.

O ● Divert blood from internal organs to the skin,

which darkens skin colour.

O ● Begin fast pantingHigh relative humidity

reduces the effectiveness of evaporative heat

loss.

Can poultry acclimatise to high temperatures?

O Adult birds take about five days to acclimatise to high

temperatures. Birds are more susceptible to sudden,

large changes in temperature.

O The first very hot days after a cool spring often result in

increased incidence of heat stress.

O Some of this will be due to poor acclimatization, but

some will be due to managers being less well prepared

than later in the summer.

What are the key features of housing that protect birds from hot

weather?

OThe key features are:

O● Insulation

O● House design and location

O● Ventilation

What does insulation do?

O Insulation greatly reduces heat transfer through a wall

or roof. Even on a normal summer’s day, it is surprising

how much solar heat can penetrate a roof if the

insulations deficient.

O On a hot day, the surface of a roof can reach 600C.

Measurements have shown solar gains of up to 30

Watts per square metre (W/m2) coming through old

broiler house roofs.

O The heat is radiated from the ceiling into the house,

increasing the heat load on the birds below.

What is the recommended standard for insulation?

O The effectiveness of insulation is described by the ‘U value’ (the lower the number the better).

O The modern recommended standard U value is: ● U = 0.4 W/m2 / 0C or better.

O In new, clear span buildings, the roof space can accommodate extra insulating material, and the walls are made using composite panels.

O The U value is typically 0.35

O 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.

O Expert advice should be sought at the

design stage

OThe inlet system – Whatever the air

change capacity available, it is critical

to distribute air uniformly and at high

speed to all of the birds in hot

weather. This is particularly true for

birds finishing in the meat sector and

where there are high stocking rates.

What are the benefits of high airspeed over birds?

O High air speed is essential in heat stress relief. In

systems with lower stocking rates, the effects are

greater.

O ● Ensure that air passing over the birds from the inlets

is as near to outside temperature and humidity as

possible.

O ● Remove the boundary layer of hot air around the

birds, aiding convectional heat loss.

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

rate

O ● Remove humid air from around the birds’ heads,

making panting more efficient.

O ● Imparts a sense of windchill to the birds. This makes

birds feel cooler than the actual temperature.

O Birds in one house might stop panting when in an

identical house, at the same temperature but with

slower airspeeds, the birds keep panting.

O ● Makes the most of evaporative heat loss when, at

very high temperatures (> 32 C),

O the effects of windchill diminish

What are the recommended air speeds over birds in hot weather?

O All meat producers should aim for between 1 m/s and

3 m/s for relief against extreme heat.

O 1 m/s should be an absolute minimum for

commercially stocked houses.

O 1.0 -1.5 m/s should be within the abilities of most

conventional powered ventilation systems, especially

after minor upgrades. (1m/s = 200 ft/min)

O To achieve 1.5 – 3 m/s, the house would usually need

to be operating in a tunnel ventilation format.

Can I use internal recirculation fans if air speeds are inadequate?

O Internal recirculation fans can play an important role where air speeds over birds are poor.

O It is important to distinguish between recirculation fans, which do not change air, and the main ventilation fans that do.

O However:

O ● The air movement generated is at house temperature and humidity.

O ● Air distribution is uneven and birds sometimes huddle into the discharge air plume, increasing stocking rate under the fans.

O ● Always consider the possibility of modifying the inlets to increase air speed evenly – this might also require an increase in air change capacity.

the disadvantages of evaporative cooling

O The disadvantages are that:

O ● In extremes of very high temperatures and very high humidities, cooling systems

O might be ineffective or detrimental.

O ● There is about a 4.5% RH increase for every 1 C of cooling. A water supply that

O 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.

O ● Should cooling not prevent heavy panting, the resultant increase in % RH can

reduce panting efficiency and increase the risk of heat stress.

O ● A cooling system cannot replace the need for high air speeds from the existing

O ventilation system.

O ● Incorrect positioning of nozzles can result in poor cooling and wetting of litter.

O ● They require frequent maintenance, especially in hard water areas.

O ● There is limited expertise or cost benefit information available.

Does reducing feed intake or feed removal help in heat stress relief?

O Birds in hot environments reduce feed consumption

naturally, reducing heat from metabolism. Feed

conversion efficiency and growth rate is also reduced.

O Techniques that increase activity or stimulate food

consumption may be counterproductive.

O Feed removal prior to the hottest part of the day has

been shown to be beneficial in reducing mortality.

O The advantages are reduced metabolic heat output, and

where feeds systems can be lifted, increased floor

space and improved air distribution over the floor.

Why is fasting benefcial during heat stress?

O In addition to heat-stress mortality, economic losses associated with broiler heat stress also occur as a result of lowered growth rate and decreased feed efciency. Terefore, it is natural for producers to want to stimulate feed consumption in hot weather. However,

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

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

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

O Fasting reduces the heat production from digestion,

absorption and metabolism of nutrients.

O 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.

O 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.

Can cool water alleviate heat stress?

OWater is lost from the lungs when

birds pant and so more water needs

to be drunk to prevent dehydration.

OCool water stimulates water intake.

Reducing the body temperature of

the bird is beneficial and has been

associated with reduced mortality.

In Summary: O ● Provide adequate ventilation for the number of birds

housed.

O ● Provide fast air speed over birds.

O ● High humidity increases the likelihood of heat stress in hot weather.

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

O ● Regularly maintain and test alarms and emergency ventilation equipment.

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

Results of electrolytes

O some researchers have attributed the increased

survival rates of heat stressed broilers receiving

supplemental salts such as protassium bicarbonate,

potassium chloride, sodium chloride and ammonium

chloride to the increased water consumption which

results, not to the salts

SUPPLEMENTS (MINERALS AND VITAMINS)

O 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.

O These include sodium bicarbonate (NaHCO3), potassium chloride (KCl), calcium chloride (CaCl2), ammonium chloride (NH4Cl) and vitamin C (ascorbic acid).

O Sodium zeolite and aspirin are also beneficial in reducing the effects of heat stress

O in laying hens

O Suppression of growth can be partially alleviated by

supplementation of

O 1% NH4Cl 0.15% - 0.6% KCl 0.2% NaHCO

O 3. Supplementation of probiotic lactobacillus strains may enrich

diversity of micro flora in chicken.

O • The addition of NaHCO3 and KCl to feed or drinking water

reduces negative effects of heat stress.

O • The addition of vitamin C to drinking water or feed helps to

reduce corticosterone levels during heat stress.

O • Aspirin also decreases corticosterone levels and can be used

when allowed by legislation.

O • Betaine results in an improved performance during heat stress.

O • Although litter quality is usually not an issue during summer, it is

advised to use products that improve gut barrier function / reduce

intestinal bacterial activity (e.g. strong anti-oxidants, butyrate,

medium chain fatty acids).

O Vitamin C

O Under heat stress, birds are not able to synthesize

the sufficient amount

O of vitamin C.

O Vit C @ 1000mg/kg Supplementation of ascorbic

acid.

O Heat resistance Carcass quality.

O Carcass weight. Carcass CP content.

O Act as antioxidant reduce oxidative injuries.

O Reduce mortality.

Electrolytes & others reduce

heat stress

NH4Cl

CaCl2

Betaine

KCl

NaHCO3

Sodium zeolite

Aspirin

vitamin C

A- DRINKER SYSTEM MANAGEMENT OF THE HEAT-STRESSED FLOCK

O 1- Ensure that drinkers have suffcient water flow (>

70 ml/minute/nipple drinker)..

O 2- Cooler water will help reduce the birds’ core

temperature and thus reduce the impact of heat

stress.(may add ice to water)

O 3- Cooling drinking water by flushing water lines

during the afternoon has been shown to increase

feed consumption and sustain egg production in

heat-stressed layers.

O 4- Keeping water below 25°C will help maintain higher

water intakes and therefore encourage higher feed

intake. Water temperature above 30°C will negatively

impact water intake and have further negative impact

on feed intake.

O 5- Use vitamin and electrolyte supplements in the

drinking water to replenish the loss of sodium, chloride,

potassium and bicarbonate in the urine. Electrolyte

supplements are best used in anticipation of a rapid

rise in environmental temperature.

O 6- In case chlorinated water is being used in the farm, it

is recommended to discontinue chlorination on

extremely hot days may use a substitute as H2O2.

O • Bacteria grow much more rapidly in the water

lines during hot weather. It is very important to

do whatever possible to guarantee water

sanitation (i.e. oxidation reduction potential of

greater than 700 mv).

O • Dump drinkers and flush water lines as often

as possible during hot weather to ensure water

is consistently as cool as possible.

B- MANAGEMENT OF THE HEAT-STRESSED FLOCK

O Avoid excessive activity during the hottest part of the

day.

O The hot weather is a great stress on the birds, so avoid

bothering and disturbing the birds during periods of peak

heat.

O 1 - Do not disturb the birds during the hottest time of the

day (afternoon and early evening).

O Adjust work schedules and lighting programs so that

routine work is done early in the morning or at night.

O 2- Management practices that require bird handling,

such as beak trimming, transfer and vaccinations (by

eye drop, wing web or injection), should be done in the

early morning hours.

O 3- Using roof sprinklers during times of extremely high

temperature can remove heat from the roof and cool the

inside of the house.

O 4- Do not run the feeders during the hottest time of the

day

O 5-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.

C- LIGHTING PROGRAMS FOR HEAT-STRESSED FLOCKS

O 1- 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.

O 2- Use a midnight feeding of 1–2 hours to provide an additional feeding during the cool of the night to encourage feed intake during hot weather ( in layers).

O 3- In extreme heat stress, lower the intensity of light during the hottest time of the day to reduce bird activity.

O 4- Intermittent lighting programs have also been used successfully in heat stress conditions to encourage feed intake.

D- When formulating the diet for hot weather condition

O Including oil in the diet has long proved to be beneficiary in hot climates and shows better effects than in moderate climates. For example, 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.

O Oil binds the fine particles in the feed and stimulates feed intake. Additionally, it increases the energy level in the feed, which is very important to compensate the reduced energy intake due to less feed intake during the hotter periods.

O 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

O advantage of oil is the content of linoleic acid, which improves the production and weight of the eggs.

O Poultry prefer high energy (in terms of fat calories) and low protein (2- 3 percent less than normal) diets with balanced amino acids (in terms of lysine and methionine).

O Replace 10-15 percent of feed energy normally supplied by carbohydrates and proteins with 1-2 percent vegetable oil/fats.

O Substitute 20-25 percent of de-oiled rice bran with oiled rice bran. This will not only

O ensure that the feed is rich in fat calories, but it will also prevent feed becoming dusty so making it more palatable.

O Use only fresh oiled rice bran, and keep only 1 week to 10 days’ supply to avoid oxidation of stocks.

O Supplement the layer feed with amino acids in line with feed intake. Replace DL methionine with methionine hydroxyl analogue and betaine.

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

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

O Supplementation with additives such as synbiotics,

phytobiotics, acidifiers and dextrose can also help in

alleviating the heat stress.

O there are several things to consider:

O 1-Formulate diets using highly digestible materials,

particularly protein sources.

O Metabolism of excess protein is particularly heat-

loading on the bird and exacerbates the ionic

misbalance.

O Formulate to digestible amino acid targets and do not

apply a high crude protein minimum in the formula.

O Synthetic amino acids can reduce crude protein in the

diet without limiting amino acid levels.

O 2-Increasing the proportion of energy

contribution from highly digestible lipid,

rather than starches or proteins, will

reduce the body heat production resulting

from digestion. This is known as heat

increment and is lowest with the digestion

of dietary fat.

O 3-The phosphorous requirement

increases during heat stress. Increases of

up to 5% should be appropriate under

heat stress conditions.

O 4- The ratio of chloride to sodium in the diet should

be between 1:1 and 1.1:1 in hot weather

conditions, with a target dietary electrolyte balance

(molar equivalence of Na+ + K+ – Cl-) of about 250

mEq/kg. Due to elevated electrolyte loss in hot

weather,

O Higher sodium levels may be required (0.02–0.03

% more than in non-heat stress conditions).

O Care should also be given that water is not

providing a significant level of chloride to the birds.

O 5- Increase the digestible lysine (and other amino

acids) to energy ratio with 5 to 10 % in heat-

stressed birds.

O 6- Due to the reduced feed intake E vitamin and

trace mineral intake is also reduced, so Vitamin

and mineral premixes should be increased by 25

percent, with particular attention paid to vitamins

C, A and.

O Many of these micro nutrients, particularly B

vitamins and antioxidants, may be beneficial to the

bird in heat stress conditions.

O Vitamin C at 200-300 mg/kg of diet can be added

to the diet to improve performance.

O 7-Organic zinc may improve shell quality by

assisting the activity of the carbonic anhydrase

enzyme, as zinc is a key mineral element of this

critical enzyme.

O 8- Organic copper may also be helpful, by

reducing the negative antagonism between

inorganic copper and zinc sources during

digestion.

O 9- Do not use nicarbazin (anticoccidial drug) during hot

weather, as it can increase heat stress induced

mortality.

Nutritional strategies for heat stress

Reduce fiber

content phosphorou

s requirement

increases

Replace carbohydrates

for oil

reduce crude protein

Higher Na levels (0.02-0.03)

Organic zinc

Water CL lysine

Organic copper

Antioxidants

Vit E

B vitamins

Vitamin C

no nicarbazin

E-HOUSING CONSIDERATIONS DURING HEAT STRESS

O Evaporative Cooling Sprinklers are commonly found in turkey barns for evaporative cooling, which are used when temperatures are more than 79-86oF (26-30oC) and the barn air is very dry.

O Too much water can actually increase the humidity of the barn to dangerous levels.

O Remember, high temperatures and high humidity make heat dissipation by evaporation very difficult.

O Death due to heat exhaustion will occur more quickly if both temperature and humidity are high.

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

O 1- Clean and ensure function of fan louvers.

O 2-Fan belts should be tightened or changed to avoid slipping or breaking during periods of high temperature.

O 3- Remove light traps during production period to increase fan capacity to maximum

O 4-Air inlets must be adequate to supply the airflow needed to ventilate the house during warm weather. Inadequate inlet space will throttle down the fans and decrease airflow.

O Inlets should be kept clean and free of anything that might restrict the flow of incoming air. Use baffle boards to direct incoming air onto the birds.

O 4-Thermostats should be checked for accuracy. An auxiliary power system must be in place in case of a power outage during hot weather.

O 5- In houses equipped with evaporative cooling systems,

the pads should be cleaned or replaced when they

become clogged.

O Water flow over the pads should be uniform with no dry

areas. Air will flow preferentially through dry areas since

there is less resistance.

O 6-Check the water filters and change if necessary. A

clogged water filter restricts the flow of fresh drinking

water into the house.

O 7-Clean spider webs and dust from window screens

frequently to improve ventilation inside the house.

O 8-Roof reflectivity can be increased by cleaning and painting

the surface with metallic zinc paint or by installing an

aluminum roof

O • Plastic or wooden baffles should be used to force the

moving air downward to ensure that the birds receive the

maximum advantage.

O • Make sure fan belts are tight. A loose belt can reduce fan

efficiency by 30 percent or more.

O • Replace old fan belts. If the sides of the fan belt are worn,

the belt will tend to ride lower in the fan and motor pulleys,

decreasing the speed at which the fan rotates.

O A reduction in fan speed of 10 percent will decrease the

airflow by 10 percent.

O Shutters and/or screens on air inlets need to be cleaned

daily or as required to allow maximum flow of air.

Heat stress management through DEB

O Heat Stress Management is directed at the reduction of wasted production. An estimation of the deviation from the desirable value for the equation [Na+ + K+] - [Cl- + S=] may be made from the knowledge of the composition of the ration.

O Supplementation of electrolytes via the drinking water or feed can then be made to restore the ionic situation to the desired levels.

O There are a number of factors which may complicate the picture. Such as:

O 1- The majority of added phosphate in feeds is acidogenic.

O 2 - The chloride salts of many added vitamins and amino acids also distort the formula's positive value.

O 3 - the natural variation of K+ ( Potassium) in the feed may be quite large (and this is a Key Electrolyte).

O Concurrent medications might influence the balances.

Osmoregulation under heat stress

Dietary Electrolyte Balance O The dietary electrolyte balance (DEB), also known as

acid-base balance is probably more critical at high temperature than at normal temperature, and different results have been reported on the most appropriate DEB for birds under high temperature conditions. Very high (360mEq/kg) and very low (0mEq/Kg) DEB can result in metabolic alkalosis and acidosis, respectively. Very high and low DEB should be avoided during diet formulation The birds under heat stress will perform best at a DEB of 250 mEq/Kg (Ahmad and Sarwar, 2006)

F- REARING CONSIDERATIONS TO COUNTER ACT HEAT STRESS

O Early heat conditioning (EHC) seems to be one of the

promising methods in enhancing heat resistance of

broiler chickens.

O Early heat conditioning refers to the practice exposing

broiler chicks to high temperature (36°C) for 24 h at 3

to 5 d of age (Lin et al., 2006). Where possible, and in

particular in older broiler houses with less efficient

ventilation, it is sound practice to reduce stocking

densities in the summer Several nutritionists

recommend

O the administration of 1g ascorbic acid/liter drinking

water throughout heat periods

O The detrimental effect of heat stress on egg production

can also be alleviated by dietary supplementation of

Vitamin A (8000 IU/kg diet)

O Vitamin E supplementation is beneficial to the egg

production of hens at high temperatures and is

associated with an increase in feed intake and yolk and

albumen solids

O Heat stress could induce the unfavorable changes in

indigenous bacterial micro biota

O The supplementation of probiotic Lactobacillus strains

may aid in restoring the gut microbial balance of

chicken having suffered heat stress .

OReduce the thickness of the old

built-up litter. Two inches of

fresh litter may be provided in

the place of old litter.

Resources

O Heat stress in poultry solving the problem

DEFRA

O Hyline article heat stress

O WWW.Heat stress.info

O Other presentations and trials