Whitepaper: Navel practicalities
Written by Maciej Kolańczyk, Senior Hatchery Specialist Pas Reform
A well-closed navel is one of the most important and easily visible signs of chick quality. In a good quality chick, the navel is well hidden in the down. One needs to blow to see it. Running a finger over it, you will hardly feel it – it is smooth and dry. It is light coloured, similar to the surrounding skin. These qualities are not always found, however. Even chicks hatched from eggs incubated under excellent conditions may still have poor navels.
A chick's navel is the residue of the entrance through which first the small intestine and then the yolk are absorbed into the body cavity. Absorption begins on day 17 and continues until day 20, making these three days critically important. The closure of the navel requires optimal synchrony between the embryo's physiology and the development of the morphological structures. Chicks hatched from long-stored eggs or from eggs produced by older breeders often show poor navels, which is probably due to disturbed synchrony.
The closure of the navel is a process that requires time and a stable, comfortable environment. Any interfering factors, such as too high or too low temperature or poor ventilation, should be avoided. These are an indication of the importance of conditions at transfer and in the hatcher.
However, other factors may cause poor navel quality too. If there is insufficient water loss during incubation, the belly will be too full to absorb everything and too stretched for the navel to be able to close. Suboptimal incubation conditions (e.g. chronically too low, or too high temperature) reduce utilisation of the yolk sac, as a small, underdeveloped embryo is not able to absorb the big yolk residues. A similar problem arises if the chicks are pulled out too early or if the hatch window is very large. Late hatching chicks will simply not have enough...
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