News Stories
Heat causes chicken death
by Fred Besari (26/01/10)
Heat stress can cause sudden death to broiler chicken if farmers are not careful in their attitudes towards raising chicken under village conditions in the lowlands of PNG, according to NARI's Livestock Programme in Lae, Morobe Province. An assessment report by the programme states that the comfortable ambient temperature range, or the thermal comfort zone, for chicken should be between 4ºC to 27ºC with relative humidity below 50%. When the temperature exceeds 27 ºC, chicken typically react to the emerging heat 
stress conditions by eating less food and increasing their respiration rate and panting.
The assessment was made following reports of an unusually very high sudden death of large numbers of broiler chicken in a commercial broiler farm in the Gobari area outside Lae city. Livestock officers visited the site and carried out the assessment which includes inspecting the environment, conducting individual interviews and testing of drinking water supplied to the chicken. The incident happened in a recently constructed large commercial broiler shed. It was noted that a large number of grown out (5 weeks old) broilers died during peak ambient temperature of an unusually hot day between 2:30pm and 4:30pm. In-house temperature was not recorded at the time but it was estimated to be above 30ºC. The day had a clear sky with no cloud cover. No shade trees were seen around the house to reduce the intense heat from the sun. The floor was not concrete, which could have provided cooler bedding. The quality of drinking water was good and did not have hazardous elements. The cause of deaths was therefore attributed to heat stress.
A similar incident was also observed on an experimental broiler flock at NARI's Labu livestock research station in Lae. The ambient temperature of that incident was over 34ºC.
The report states that when temperatures exceed 27ºC, chicken also increase their water intake up to five times the amount of water they would take under normal conditions. They seek wind and cooler locations in the house. Extended heat stress on chicken leads to reduced growth for broilers and lower egg production for layers. Fertility will also be negatively affected. These continue until their body thermoregulatory system, which operates to maintain healthy core body temperature, breaks down. Beyond this point, the body’s physiological balance is upset and the birds become inactive and eventually collapse instantly and die.
The commonest preventive measures are reducing access to feed, increasing air movement through ventilation and opening up aeration vents around the house, increasing supply of cool drinking water, and if possible sprinkling the birds with cool water along with fan ventilation. For commercial flocks, it is advisable to add supplementary electrolytes in the drinking water to restore lost electrolytes through evaporation.