High Environmental Temperature & Management of Poultry Birds

Dr. Rekha Bhatt

Product Manager, Mankind

Table 1. Heat Stress & Ambient Temperature
12.78-23.89 °C (55° to 75°F)	Thermal neutral zone. The temperature range in which the bird does not need to alter its basic metabolic rate or behaviour to maintain its body temperature.
18.33-23.89 °C (65° to 75°F)	Ideal temperature range.
23.89-29.44 °C) (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 temperature reach the top of this range.
29.44-32.22 °C (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.
32.22-35 °C (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.
35-37.78 °C (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.
>37.78 °C (Over 100°F)	Emergency measures are needed to cool birds. Survival is the concern at these temperatures.

Two way strategy of bird

• Activation of Insensible Heat Loss Mechanism (Evaporative cooling)
• Panting (Open mouth breathing) to get rid of body heat through evaporation of body water.
• Increased gaseous exchange rate (expiration of CO2 and O2) and thus decrease in blood CO2
• Maintenance of blood CO2 concentration
• H+ + HCO3              H2CO3               H2O + CO2
• Respiratory alkalosis, Disturbed acid-base balance, Ionic balance (Na, K, Cl)
• Decreased carbonate ion, disturbed eggshell formation, calcium metabolism, etc.

• Decrease metabolic heat production
• Decreased feed intake and thereby decreased nutrient intake (Energy, protein, vitamins and minerals, etc.)
• Negative nutrient balance 
• Mobilization of body reserves for maintenance
• Increased water intake

Signs of Summer stress in poultry

• When birds are in summer stress condition, they pant with opened mouth, spreading their wings and squatting on the brink of the bottom (Gasping, panting, spreading of wings, pale combs and wattles, closed eyes, lying down, drop by egg production, increased cannibalism and decreased appetite (Safdar and Maghami, 2014).
• Attempt to move faraway from other birds or move against cooler surfaces, like the block walls or into moving air streams. Water consumption increases and feed intake decreases. Lift their wings far away from their bodies to scale back insulation.

Table 2. Methods of Sensible and Latent Body Heat Loss
Heat Loss Method –	Direction of Heat Flow
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.

Adverse effects of heat stress in poultry

Various physiological and pathological changes that take place in the flock, during high summer temperatures.

• Energy intake and thereby feed consumption and other nutrient intake reduce as the environmental temperature increases. Consequently, the growth rate and body weight of birds will become lower. Also, there is reduced egg production in layers.
• There will be an early two-fold increase in the water consumption of birds during summer; because during high environmental temperatures, the major way to lose the excess heat produced in the body is by loss of water vapour through expired air.
• High ambient temperature increases the respiratory rate and body temperature. Since there are no sweat glands in Poultry, they will start panting vigorously, in order to lose the excess body heat produced. As the outside temperature increases the heat production as well as the heat loss from the body decreases.
• For every 1^oC increase in ambient temperature, the heat production in the body decreases by about one percent. On the other hand, water loss through respiration increases with the increase in ambient temperature.

• High environmental temperature on the other hand decreases oxygen consumption, blood pressure, pulse rate, thyroid size and activity, blood calcium level and body weight.  
• During panting, there is an increase loss of CO ₂ and a decreased hydrogen ion concentration resulting in increased pH (alkalosis) according to the reaction: HCO^–+ H⁺               H₂CO₃                CO₂ + H₂O. The change in acid-base balance and the decreased feed intake have been reported to be the main factors responsible for poor performance of heat stressed chickens. The loss of CO₂ also reduces blood bicarbonate concentration and this is probably a major factor affecting the rate of lay and egg shell quality of heat-stressed laying hens.
• The problems with ecto-parasites will be more during summer and the following monsoon.
• The high environmental temperature associated with high relative humidity (>70%) may lead to outbreaks of Coccidiosis.
• Incidences of Fatty Liver Haemorrhagic Syndrome and other metabolic disorders like heat stroke, liver rupture etc. are more during summer; especially in case of heavy broilers.
• Birds will shed more feathers during summer, in order to lose the excess body heat produced.
• At high environmental temperatures, nearing the body temperature of the birds, vaporization of body water through respired air is the only way to lose substantial amount of heat from the body. However, this is possible only when the inspired air has very low moisture levels. But if both temperature and relative humidity are high, birds will not be able to lose the excess body heat and will finally die of heat prostration.
• Fatty birds succumb first, perhaps because their air sacs are rather constricted and thereby not able to evaporate moisture and produce coolness efficiently.
• Caged birds and birds reared on slatted floors will suffer more due to high environmental temperature than birds reared on litter floors; because birds on litter can cool themselves to some extent by dusting themselves in the litter.
• Heavy mortality due to heat stroke will be noticed among heavy broilers, in the late afternoon and evening.
• Temperature affects egg breakage. Elevated environmental temperature is associated with a decrease in shell quality. The reduction of shell thickness produced by heat stress is apparently due to respiratory alkalosis which causes a lowering of partial pressure of carbon dioxide in the lungs and raises blood pH (Farnell et al., 2001).
• As the ambient temperature increases above 26^oC, the egg size declines.
• Reduced fertility rate due to a) poor semen quality, b) Reduced mating frequency and c) Higher incidence of female infertility. Production of poor-quality chick.

Management steps that can help birds combat heat stress:

• Water management is crucial in heat stress management. In summer, water consumption goes up 3-4 times feed intake. So, a good quality water supply is essential. A water hygiene process must be followed because bad bacteria can prevail rapidly under poor conditions, which will lead to disease conditions. Water pipelines must be cleaned well and flushed with organic acids or hydrogen peroxide periodically. Treat water with a quality water acidifier and sanitizer. In general, try to make the water pH in acidic conditions (5.5-6). As feed intake is less during times of increased temperatures, nutritional water acidifiers should be used to help combat heat stress.
• Housing management can be divided into two parts, inside shed management, and outside shed management.

Outside the shed

• Thatching of the roof with green grass or agricultural waste can help reduce shed temperature. Paddy straw can be used for this purpose.
• Whitewashing the roof with lime helps mitigate the temperature inside the shed.
• Applying sprinklers above the shed.
• The use of gunny bags on the side walls (grill) of the shed over which drip water is set.
• Allowing trees to grow near the shed to provide shade on the shed.
• Prohibit wild birds, which can carry diseases like Avian Influenza, from entering the shed.
• Provide 4-6 feet of roof overhang to protect birds from direct sunlight.
• Provide ridge ventilation to help remove hot air from inside the shed.

Inside the shed

• Use of fans
• Use of a fogger
• Provide a continuous supply of cool water (if not possible, periodically flush the water to provide cooler water for birds)
• Reduce litter thickness (ideally around 400-450 grams per square foot)
• Feeding Management

Research shows feed intake is reduced by 1.25% with every 1°C rise in temperature. Further, it is observed that there is a decline in feed intake by almost 5% with every degree rise in temperature from 32-38° C. Knowing this it’s best practice to feed a good quality feed during times when heat stress can occur.

• Feeding should be done during the cooler hours of the morning or evening but too much gap in feeding time is not advisable.
• Increase the number of feeders and drinkers during feeding time to reduce competition among birds.
• Electrolytes and vitamins supplementations alleviates the adverse effects of HS. Supplementing the drinking water with Na , K and Cl salts were attributed to increased water consumption which facilitates heat dissipation and cools down the body (Smith and Teeter, 1988) and normalization of blood electrolyte balance. Supplementation of the drinking water with vitamins A, D, E and B complexes has been found to improve performance and immune function of broilers under HS.

• Adding antioxidants is shown to be helpful to reduce stress and improve feed consumption while maintaining or improving body weight gain. (Vitamin E, Vitamin C, Selenium).
• A high-energy diet should be provided during summer because birds lose more energy while panting.
• Energy in feed should be supplemented with oil rather than grain because fat has the lowest heat increment value compared to carbohydrates and protein.
• Feed consumption is reduced in summer. To overcome nutritional and productive losses it is suggested to supplement the diet with 10-15% more amino acids, vitamins, and minerals rather than increasing the protein level directly.
• Increase calcium and phosphorus levels to overcome thin eggshells more often seen during summer due to respiratory alkalosis (more carbon dioxide is lost due to panting).
• Instances of viral challenges increase during this time as immunosuppression is common. immunity boosters (Vitamin E, Selenium, Zinc –BIRDICARE), Vitamin C can help to reduce stress and improve the performance of the flock.
• Essential oils have a broad range of action from being immunomodulators to performance enhancers. Adding essential oils (RESPOHERB LIQUID) in the form of spray or drinking water can help mitigate respiratory challenges during summer stress and improve immunity and overall performance.
• The addition of ammonium chloride, potassium chloride, and/or sodium bicarbonate has shown improved performance in broilers by improving water quality and feed intake.
• Probiotics can be used to help control the corticosterone level and the excessive release of pro-inflammatory agents. Lactobacillus-based probiotics enhance goblet cell count in the duodenum and jejunum of heat-stressed broilers thereby improving the feed conversion ratio.
• Since a hot humid climate favors the growth of mould/fungi in feed the consistent use of an antifungal is recommended.
• General Management
• The depth of litter should be 2-3 inches on the floor.
• 10% extra floor space should be provided in summer. Bird overcrowding only contributed to heat stress and must be avoided.
• Shifting, transportation, debeaking, and vaccination should take place during the night or cool hours in the morning.
• Birds severely heat stressed may be dipped in cold water for 2-3 minutes to provide relief. Be sure to keep their head and neck above the water level.
• Use foggers in the shed, which can reduce the shed temperature up to 5-10°C depending on the quality of the fogger.
• The house should be situated away from other buildings to facilitate the free movement of air.

“Summer management is crucial not only to improve the performance but to gain profit in adverse conditions. So, effective use of feeding, Water, shed management brings the good health of birds and thereby profit to the farmer”.