Heat stress: A matter of life and death importance?

Roos Molenaar, M.Sc.

In practice, high incubation temperatures at the end of incubation are often observed. Embryos experience high temperatures due to cooling and air velocity problems in the incubator, especially during the second half of incubation when heat production increases. Heat production of high yielding breeds has been increased over the years and increases the risk of overheating even more. Is this a matter of life and death importance?

The first signs of overheating can be observed when the hatcher is opened for processing and birds pant and are noisy. An other indication of overheating is small chicks with large residual yolks. The high incubation temperature reduces incubation time and, therefore, time to develop. When process time is fixed, birds spend more time in the hatcher and loose more water due to evaporation. Other signs of overheating are red hocks and red beaks, because birds struggle to emerge from the eggshell due to a higher incidence of malpositions in the egg. Heat stressed birds often have unhealed navels, as a result of the reduced incubation time and the large residual yolk that needs to be retracted in the body cavity during the final stages of incubation. Download the entire article via the button below.