Heat stress is currently a problem in broiler production and causes a decrease in meat production. In this research an existing thermoregulation model for beef cattle was adapted into a thermoregulation model for broilers in conventional production systems in The Netherlands.
Genetic selection has increased the growth rates of broilers tremendously, which increased broiler heat production. Because of increased heat production, heat stress is currently a problem in broiler production and causes a decrease in meat production. It is currently unknown what combination of climate conditions in the stable causes heat stress. This thesis focuses, therefore, on adapting an existing thermoregulation model for beef cattle into a thermoregulation model for broilers. This has been done for broilers in conventional production systems in The Netherlands.
Broilers dissipate heat via different routes: respiration, latent heat release, long wave radiation and convection. This thesis investigates the effect of ambient temperature, air velocity and relative humidity on heat dissipation. The developed model for broilers is validated with recommended climate conditions from literature. Also the interaction between the climate conditions has been investigated, as this is currently unknown.
In the first three weeks of life the broiler has as high body area: body volume ratio. Model simulations confirm that the recommended ambient temperature needs to be between 32 and 35⁰C. Air velocity needs to be low, 0.5-1 m/s, otherwise the young broiler will dissipate too much heat. After the third week of life, the body area: body volume ratio has changed, so the recommended temperature needs to decrease to 22⁰C and air velocity needs to be increased to 2 m/s. Relative humidity needs to be around 60%. If temperature and relative humidity are both high, the broiler is not able to lose much heat via respiration, which is the main route of heat dissipation when a broiler is in heat stress. The recommended climate conditions from literature are in general in line with the thermoregulation model.
It has been shown that the climate conditions have a big influence on the heat flows. Besides that, it has been shown that the interaction between temperature and air velocity and the interaction between temperature and relative humidity is crucial to avoid heat stress in broilers. Small changes in climate factors can influence thermoregulatory processes of the broilers. These factors, therefore, need to be taken into account simultaneously.
Student: MMA Brouwer
Supervisor: A. van der Linden, MSc