Source: Elizabeth Griebel, ANR Extension Intern for Wright, McLeod, and Meeker Counties
In poultry, heat stress can quickly become fatal as temperatures increase due to the poor natural heat loss exchange in birds. It is important to measure external temperature and humidity as both play a role in heat stress. Please see Iowa State University’s Heat Stress Indices for Livestock for indexes on temperature and humidity. Birds are most comfortable at 60 to 70 degrees F. From 75 to 85 degrees F, with increasing humidity, they begin to decrease feed intake and production, panting, and have behavioral changes. At 85 to 100 degrees F, the heat gain exceeds heat loss and relief is needed.
Chicken and turkeys will display heat stress by having lower feed intake and weight gain. Heat stress can lead to lower laying performance and cause a decrease in egg weight and shell thickness. Heat stress often results in panting, and increases in water intake, however, this may not be enough to maintain the losses through respiration and urine excretion, which can become fatal for birds. Heat stress can also result in lower feed efficiency. Most birds prefer to eat in the morning, which can increase their risk of heat stress as digestion increases the internal temperatures of the birds. Withdrawing feed 6 hours before an increase in humidity and temperature can reduce this risk of heat stress in poultry.
According to the Heat Stress Indices, as humidity increases above 50%, birds begin to enter the danger zone. 90 degrees F and 50% humidity is an extreme risk to poultry. Birds will generally try to lose heat by panting, however, panting creates more heat through muscle activity. Heat stress can worsen in birds with contact with warm surfaces such as concrete floors, bare ground exposed to direct sunlight, and overcrowding of other birds.
Mitigation strategies look different in each operation, key components for reducing heat stress are promoting good ventilation and movement, and having fresh and cold water available at all times. In confinement spaces, there are many ventilation options, tunnel ventilation, fans, or evaporation cooling in high heat conditions to minimize heat stress.
Additional key points to prevent heat stress:
- Having cool, fresh water readily available
- Including electrolytes and/or vitamins such as A, D, E, and B complex - these can be supplemented in the water
- Providing sodium bicarbonate is important for hens in egg production
- Withdrawing feed 6 hours before peak temperatures in the afternoon
- Increasing airflow and ventilation
- Having shade available for birds that are outside
- Minimize movement, delay moving birds during the warmest parts of the day
- Reduce overcrowding
Learn more about managing and reducing heat stress in your poultry operation.