A hatch breakout analysis involves opening unhatched eggs (Dead-in-Shell) to determine at what stage of incubation embryo mortality has occurred. A hatch breakout is a useful tool for solving hatch problems and looking for areas to improve hatch performance.
For a breakout analysis, five sample setter or hatcher trays per breeder flock and hatch should be identified. The trays should be chosen from different positions within the incubator and the number of eggs per tray should be recorded.
At fertility testing, open all eggs removed from the sample trays as clear or early dead germ. Do not refill the trays after fertility testing.
During hatch take-off, the number of culls and cracked eggs on each sample tray should be counted and all unhatched eggs opened. The results should be recorded on a record sheet to form part of the interpretation. Mortality must be expressed as a percent of eggs incubated.
Record whether the hatch debris was clean or dirty, the poults were still hatching (wet poults still on tray) or if poults were very thin as this provides clues as to advanced or late hatch.
A suggested staging for embryos:
1. Record any malpositioned embryos:
2. Record any abnormalities.
3. Record any contamination.
4. Record any cracked eggs.
An example of a complete Dead in Shell Record Form is shown in Figure 1, each line represents one hatcher tray.
Interpretation of Results
Results from a hatch breakout should be combined with other information to provide a total picture. This information should include hatchability records, breeder performance records, incubation records and hatch timing information.
In a good hatching flock there are two main periods of embryo mortality: 3 – 10 days and 25 – 27 days + pips. High mortality at other development stages is not normal. A high incidence of mortality at a particular stage of development can indicate an acute problem during incubation caused by a machine failure.
A chronic problem, such as slight overheating, may result in mortality later in incubation.
Specific embryo abnormalities can be associated with specific problems (nutritional, incubation, toxins and disease) but it is important to note that the same abnormality can be the result of more than one problem. For example eye cataracts have been associated with high incubation temperature, mycotoxins and vitamin E deficiency.
Experience of hatch breakouts with good hatching flocks is important for understanding what is normal and abnormal.