Dr. Anvesha Bhan, Dr. Sundus Gazal and Dr. Sabahat Gazal
Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, J&K, India
Poultry is one of the crucial industries that count for high-quality protein production.Today, India is the third largest egg producer and the sixth largest meat producerin the world. The most obvious constraint on poultry production is the hot and humid climate andthe high ambient temperature of the birds. Heat is produced by metabolism within the body, which includes maintenance, growth and egg production and is affected by body weight, species and breed, level of production, level of feed intake, feed quality and, to a lesser extent, by the amount of activity and exercise.
The internal body temperature of domesticated chickens at 41.2°C to 42.2°C is measurably higher than that of livestock and humans (36°C to 39°C). Poultry are not well adapted and disposed to high ambient air temperatures as they lack sweat glands in the skin.
General guide to the reaction of adult poultry to various temperatures 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. 65 ° to 75°F Ideal temperature range 75° to 85°F A slight reduction in feed consumption can be exp 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 shape 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.
Heat can be lost in a variety of ways. Three normal methods of heat loss are:
1. Radiation – Heat will be lost from the body if the surrounding surfaces are below bird’s surface temperature. Conversely hot walls and roofs may radiate heat to the bird surfaces
2. Convection – Heat loss will occur from the natural rise of warm air from around a hot body. Providing moving air can assist convection, but only if the air moves fast enough to break down the boundary layer of still air that surrounds the body.
3. Conduction – Heat will transfer from one surface in contact with another surface, for example, if the birds are seated on litter that is cooler than their bodies. However, the litter immediately under the birds soon assumes a temperature close to that of the body.
4. Evaporation – This is very important at high temperatures as poultry do not sweat but depend on panting and effects only if the humidity is not too high.
Birds will try to re-establish their heat balance with the surrounding by changing their normal behaviour by: Trying to move away from other birds; move against cooler surfaces, such as the block walls or into moving air streams; lift their wings away from their bodies to reduce insulation and expose any areas of skin that have no feathers; elect to pant slowly;rest to reduce heat generated by activity; reduce feed intake; increase water consumption; divert blood from internal organs to the skin, which darkens skin colour and begin fast panting
When bird start panting, there are many consequences like:
1. Heat is lost as moisture is evaporated from airways in the birds.
2. Panting requires muscle activity, requiring energy use that generates some additional heat.
3. Respiration rate can increase by as much as 10 times the resting rate.
4. High relative humidity reduces the effectiveness of evaporative heat loss.
5. Increased respiration rate results in loss of carbon dioxide and a rise in blood plasma pH (called respiratory alkalosis). Blood potassium and phosphates are depleted, sodium and chloride levels increase.
6. Growth rate or egg production will reduce.
Measures to alleviate heat stress in poultry:
· Housing Management:
1. Housing: To minimize heat-stress-related problems during hot weather, it is always beneficial to insulate poultry-house roofs/ceilings. Minimum level of ceiling insulation for a naturally ventilated 2 house is R-value 1.25 m C/W. Whereas houses that have high temperatures above 2 40°C or temperatures below 0°C typically require ceiling R-values of 2.25 m C/W or more. There are a variety of methods of insulating a poultry-house ceiling dropped ceiling, rigid board insulation, spray polyurethane insulation, reflective insulation etc.
2. Air movement: It increases convective heat loss from the birds in a house, thereby lowering the effective air temperature and helps to remove trapped heat from between the birds as well as from cages. Last, but not least, it lessens the adverse effects of high-humidity environments.
3. Recommended air speed: All poultry producers should aim for between 1 m/s and 3 m/s for relief against extreme heat.
4. Ventilation: These include curtains, fans, fogging nozzles, evaporative cooling pads, timers, static pressure controllers, thermostats etc.
5. Evaporative cooling: This can be achieved by two ways: Fogging systems and pad systems. Pad systems can only be installed in a power-ventilated house, fogging systems can be used in either powerventilated or naturally ventilated housing to lower house temperatures during hot weather. A third system, sprinkling, has limited usage except in very dry climates.
6. Foggers: Reduces air temperature in the house on hot days (90 o to 95 F) when humidity is low, especially during mid-day when humidity levels are lowest and temperature is highest
· Nutritional Management:
1. 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 second alternative is to feed the birds at the time of day when feed consumption is highest. If birds are fed during the cool part of the day, feed consumption will be higher.
2. Drinking water: Cool water (at 10-12OC) should be supplied continuously to birds. Watering space should be doubled. Over head tanks and pipe system should be properly covered to keep the water cool. Adding an electrolyte to the drinking water will replenish vital nutrients that will help balance blood pH levels. Offering a night-time feeding program will encourage birds to eat during cooler periods and help maintain their performance during hot weather.
3. Electrolytes: Sodium bicarbonate in the feed or use of carbonated water is especially useful for hens in egg production. Panting and carbon dioxide release can change the acid-base balance in poultry, but also the bicarbonate available for eggshell formation. Thus sodium bicarbonate can help lessen these changes.
4. Energy: The concentration of energy should be increased by 10% during heat stress, whilst the concentration of other nutrients should be increased by 25%. Feed intake changes about 1.72% for every 1°C variation in ambient temperature between 18 and 32°C.