Dr. Ebibeni Ngullie
ACTO (Animal Science), KVK Dimapur
Research Fellow, KVK Dimapur
In India there are zones having climate ranging from 40oF to 85oF during winter. The optimum temperature in a house is 65-75oF, when the temperature drops below 45oF steps must be taken to warm the house.
1. Chick mortality due to lowered temperature
2. Most of the energy used by the birds maintain their body heat, thus retarding its growth
3. Combs become cyanotic
4. Birds do not reach peak production during the expected period
5. Sexual maturity is delayed in pullets and these birds turn out to be poor layers
6. Birds consume more feed to maintain body temperature
7. More moisture is retained in winter due to less evaporation and creates dampness in the house
8. If the overhang is not long enough rain water can splash in and cause a wet litter problem
9. Houses must be built on an elevated ground to prevent stagnation of water, which in turn cause severe disease problems
10. A lower environmental temperature increases oxygen consumption, blood pressures and thyroid size
11. Cooler temperatures are immunosuppressive and thus predispose birds to infectious agents endemic in that environment
12. Respiratory infections like CRD, infectious bronchitis, avian influenza and coryza etc. compromise the lung capacity and therefore reduce the oxygen supply through the lungs
1. Provide clean litter material and increase the thickness of litter
2. Provide good ventilation but prevent chill air from entering in
3. Seal all the cracks and crevices in the house
4. Remove all leaking waterers and repair leaky roofs
5. The overhang must be 4-6 feet in length to withstand wind and to prevent rain water from splashing inside
6. The roof height should be lowered
7. Asbestos roof may be used as they hold the warmth within the house
8. Side curtains can be used during severe winds and draft thus sealing the house from cold draft
9. Ceiling fans may be used to move hot air from the ceiling towards the birds
10. Solar heaters can be used and the energy stored and this can be used to warm the house
11. The time period for brooding chicks in cold weather will be extended to even 4 to 6 weeks
12. Oil or fat can be added to feed and energy levels in the feed can be raised to meet the higher energy need of the bird
13. Extra vitamins and minerals have to be supplemented
14. Both vitamin C and vitamin E can be given to increase the immune response
15. The feeders should always be full
16. Provide warm water to the birds
17. Prevent spilling of water on the litter
18. Increase the stocking density by 5%
In temperate countries, environmentally controlled poultry houses are in vogue. These houses are heated by electricity or gas. The blower blows in warm air and fans circulate the warm air, all this is thermostatically controlled. Gas pressures are checked, inlets and outlets open uniformly to keep the birds comfortable. Ventilation is adjusted to remove excess ammonia and to prevent increased fuel usage.
Chickens are very sensitive to environmental temperature. Their growth, egg production and health are severely affected during extremes of weather. Therefore, within the economically feasible limits, ideal temperature has to be provided to the birds, in order to obtain optimal growth rate and returns from the birds. For optimum feed efficiency, an ideal temperature range of 21oC- 24oC is needed. However in tropical climates, these temperature ranges may be obtained during winter only. During other seasons especially during summer, the ambient temperature goes several degrees higher than the ideal zone causing severe depression in the growth rate and egg production thereby leading to great economic loss to the poultry farmer. By proper summer management, these losses can be overcome to a great extent.
The various physiological and pathological changes that take place in the flock, during high summer temperature are as follows:
1. Energy intake and thereby feed consumption and other nutrients intake reduce as the environmental temperature increases. This is because birds need less energy for maintenance of body temperature, when the ambient temperature is high. Consequently, growth rate and body weight of birds will become lower.
2. There will be early two-fold increase in the water consumption of birds during summer; because during high environmental temperature the major way to lose the excess heat produced in the body is by loss of water vapour through expired air.
3. 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 1oC increase in ambient temperature, the heat production in the body decreases by about one per cent. On the other hand, water loss through respiration increases, with increase in ambient temperature.
4. High environmental temperature on the other hand decreases oxygen consumption, blood pressure, pulse rate, thyroid size and activity, blood calcium level and body weight.
5. The problems with ectoparasites will be more during summer and the following monsoon. Moreover, high environmental temperature associated with high relative humidity (>70%) may lead to outbreaks of Coccidiosis. Low feed intake and thereby low coccidiostat consumption will further aggravate Coccidiosis outbreaks.
6. 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.
7. Birds will shed more feathers during summer, in order to lose the excess body heat produced.
8. At high environmental temperatures, nearing the body temperature of the birds, vapourisation 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.
9. 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.
10. Heavy mortality due to heat stroke will be noticed among heavy broilers, in the late afternoon and evening.
11. Temperature affects egg breakage. Elevated environmental temperature is associated with decrease in shell quality.
12. Reduction of shell thickness produced by heat stress is apparently due to respiratory alkalosis which causes lowering of partial pressure of carbon dioxide in the lungs and raises blood pH.
13. As the ambient temperature increases above 26oC, the egg size declines.
The above adverse effects due to high environmental temperature can be overcome to a considerable extent by proper management of the flock, house, feed etc. during summer, as indicated below:
1. By proper roofing, the temperature inside the poultry houses can be kept at 5oC – 10oC below the outside temperature. Thatched roofing of about six inches thickness provides optimum comfort to the birds during summer, than any other roofing material. However, due to the risk of fire, less durability, more depreciation and rodent problem, thatched roofing is not preferred, especially by large farms.
2. In large farms, aluminium roof is preferred due to its durability, resale value and rear reflecting properties.
3. In case of non-insulated houses, the roof must be raised to a sufficient height from the floor level; because higher the roof, cooler will be the poultry house. The minimum height between the floor and the roof must be 4.0 and 3.5 metres at the ridge and eaves, respectively.
4. The eaves at the roof shall project out atleast one metre on all the four sides as over hang to prevent direct sun light and rain water entering into the house.
5. Further, where the summer is very severe, the roof may be insulated either by covering with a layer of thatch or by painting the upper surface of the roof with a white paint such as white water proof paint, or aluminium paint, to reflect the sun’s rays back and the inner surface may be painted with a black paint or tar to absorb the heat from within.
6. In tropics, in order to prevent direct sun light falling into poultry houses, the long axis of the houses have to face north and south i.e. the houses must be orientated east to west; with a slight tilt towards southern side in the east and towards north in the west. This type of orientation also prevents severe drafts and rain water sprinkling into poultry houses during monsoon.
7. Open type, cross-ventilation is recommended in tropics. Except for a 20cm height wall, all the four sides upto the roof should be provided with 12mm size and 18 gauge chicken wire mesh or 25mm size chain link mesh.
8. Sprinklers may be fixed on the top of the roof and operated continuously from 10 to 18 hours, to cool the roof.
9. Foggers may be fixed inside the broiler house and operated during hot and dry weather, to produce evaporative coolness.
10. Grow “fast-growing” shady trees around poultry houses in order to reduce the severity of the summer heat waves and also to break wind drafts during monsoon.
11. Rear relatively more heat tolerant strains of broilers suitable for tropical climate.
12. During hot weather, birds consume twice the amount of water than that is normally consumed. Therefore, double the watering space in poultry houses during summer. Provide plenty of fresh, clean and cool drinking water during hot weather. The water pipes should not be exposed to sun light. Change the water two or more times a day, if it gets heated up.
13. In order to encourage the feed intake of birds during summer, reduce the energy content of the feed by about 10 percent. It is also advisable to provide an addition of one or two percent protein and slightly increase the levels of vitamins, minerals, and essential amino acids and coccidiostat.
14. Large farms in hot and dry climate may opt for environmentally controlled poultry houses.
15. Drugs and chemicals like electrolytes, ascorbic acid, sodium bicarbonate, tranquilisers, sodium salicylate, paracetamol, chlorpromazine hydrochloride, cyproheptadine hydrochloride may be administered through feed or water, to make the birds to withstand hot weather.
16. Thick and wet litter produce/ generates more heat. Therefore, during summer, the litter thickness must not be more than 6cm. Moreover, remove caked up and wet litter immediately from the poultry house, to stop excess heat production.
17. Avoid over crowding. Increase floor space by atleast 10% during summer.
18. If mechanical ventilation is provided, increase the air flow rate and air exchanges by atleast 25%, during summer.
19. Do not disturb the birds and make them panic during hot weather.
20. For birds kept in cages, the centre height of building should be a minimum of 14 feet.
Optimal environmental conditions for rearing broilers:
Temperature: 22-30oC (70-85oF)
Relative humidity: 30-60 per cent
Ammonia: Less than 25 ppm
Litter moisture: 15-25 per cent
Airflow: Airflow should be 10-30 metres per minute