An eggshell temperature of 100°F (37.8°C) is widely accepted as optimal for embryonic development from the start of incubation up until transfer time. Eggshell temperature control in the setter has therefore become common practice to achieve optimal results. But what about the hatcher phase: Is an eggshell temperature of 100°F also the optimal setpoint after egg transfer? This article discusses the results of a Petersime trial that investigated three hatcher temperature profiles and their effect on hatchability and chick quality.
|Mean Hatch of Fertile (%)||97.4
(SD = 1.2)
(SD = 1.0)
(SD = 0.9)
* SD = the standard deviation indicates the dispersion of the sample data from the mean
The mean Hatch-of-Fertile results - summarized in above table - show no significant differences in percentage due to the eggshell temperature deviations between the moment of transfer (day 18) and the beginning of hatch (day 19 and 19 hours). However, a closer inspection (cf 2. Chick quality) will confirm that 100°F is to be considered as the optimal eggshell temperature from set to hatch.
Contrary to the expectation that even a slight eggshell temperature deviation would significantly affect the hatch percentage, the results of the trial show otherwise. The 18-day-old/19-day-old embryos coped well with the ±1.5°F deviations and succeeded to hatch. This might be explained by the evolution in embryo thermoregulatory capacity. During the first two weeks of incubation, an embryo is poikilothermic, which means it has an absolute low tolerance to any temperature deviations. As of incubation day 14, the transition to the homeothermic phase begins. At 7 to 10 days post-hatch, a new-born chick has transformed into a homeotherm organism that can regulate its body temperature within certain limits.
2. Chick quality
As it is logical to assume that an embryo facing deviating eggshell temperatures has to ‘compensate’, causing other possible issues, we have also investigated how the same eggshell temperature deviations influenced navel quality, the prime indicator for chick quality. A good-quality navel is closed, dry and free of eggshell and membrane residues. A poor-quality navel is a potential place for bacteria to enter the most sensitive part of the body cavity, which drastically increases susceptibility to diseases and the risk of post-hatch mortality.
Below is described how the ‘navel quality score’ for the trial was divided into three categories: