Tags: Incubation | Whitepaper
16 September 2014,
As a breeder flock ages, the number of 'clear' (infertile) eggs increases as a result of decreased fertility and increased early mortality. Consequently, with higher numbers of clear eggs, a higher proportion of the heat produced by developing embryos in the fertile eggs is absorbed by the 'cold' clear eggs placed around them.
Embryonic temperature in the fertile eggs is reduced by a combination of the air flowing over them, together with the 'redundant' loss of heat absorbed by the clear eggs. To achieve optimum embryonic temperature in this scenario, we can compensate for the heat 'lost' to cold, clear eggs by increasing the temperature of the warm air flowing over the eggs.
The temperature of the air flowing over the eggs is governed by the incubator's temperature set point. If air temperature is either too high or too low, the incubator controller adjusts cooling or heating rates respectively, until temperature set point is reached.
When there are more than an average number of clear cold eggs positioned between developing fertile eggs, incubation temperature should be raised accordingly - in line with rates of fertility and early mortality in each particular batch of eggs. Estimates for these rates per different flock ages should be available in the hatchery's reference data, or in the breeder's management manual.
The hatchery manager knows that there is a critical relationship between embryonic temperature, hatchability and chick quality. Incubation temperatures that are set too low will result in increased mortality and a higher number of hatched chicks with a full belly.
Optimum incubation temperatures for a batch of eggs with 65 - 75 % fertility (yellow line) and 85 - 95 % fertility (blue line) to achieve optimum egg shell temperatures (yellow dotted line)