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Chick Checking and Incubation Improvement Part 2: Analysis of Navels

23 August 2016

Analysing chick quality is a key factor for the fine tuning of incubation conditions in order to maximise the genetic potential of the hatching eggs. This article focuses on the typical defects observed on the navels of day-old-chicks and how to investigate the cause of the problem in order to optimise chick quality, writes Frank Verschuere, Hatchery Development Department, Petersime NV.

Commercial hatcheries are operating at a very high capacity. This means it is no longer possible to carefully inspect each single day-old-chick.

The analysis of chick quality should be done in a controlled way by selecting samples of specific flocks that one wants to investigate. It is important to ensure a consistent and accurate practice of the analysis.

What is a navel?

During the final stages of incubation, many important processes occur such as the blood withdrawal from the CAM (chorioallantoic membrane) and the yolk sac uptake. The navel is the physical point of this vascular and yolk sac retraction.

The navel area is one of the most vulnerable areas for bacterial and fungal infections. An infection can lead to poor post-hatch performance. Therefore it is important that the CAM and yolk sac are fully retracted, which will ensure a clean and well-sealed navel.

Clean and well-sealed navelClean and well-sealed navel

Different navel issues

The most common navel issues can be categorised into 4 groups:

  • Black button or bruised navel
  • ‘String’ navel
  • Open and unhealed navel (often with residual yolk)
  • Infected navel

‘String’ navel‘String’ navel

Eliminating external factors

Before considering modifying the incubation programme, it is critical to exclude other factors, for example bad practices of farm management, genetics, egg storage, pre-heating, transfer conditions and so on.

It is equally important to check for technical factors like calibration errors, poor loading or transfer pattern, and proper functioning of cooling, heating and ventilation systems.

More information about this can be found in the previous article of this series.

If the poor performance is regional (e.g. a certain area in the machine), the cause is often not related to the incubation programme.

Cause of navel issues

Based on the many years of on-site support, it is possible to sum up the most occurring causes of bad navels. It is however impossible to discuss all the possible causes of poor navel quality. Listed below are the most important areas to investigate.

  • Black button or bruised navel: The cause is often an incorrect transfer temperature during the late setter cycle or during transfer. An egg shell temperature of 100.0°F (37.8°C) is generally optimal. But for young, small eggs it can often result in excessive cooling whilst for very old, large eggs it can result in inadequate cooling due to different volume to surface area ratios. Different breeds have different heat production curves and factors as storage conditions, storage time and pre-heating also influence this curve, which requires programme modifications.
  • ‘String’ navel: The cause is often a poor weight loss and/or excessive cooling during the end of the setter cycle or the early hatching cycle. Excessive spraying after transfer also increases the amount of this defect.
  • Open and unhealed navel: The cause is often a late or wide hatch window and a temperature that crossed the correct temperature limits.
  • Infected navels: Generally the cause is poor sanitation and/or contaminated/floor eggs combined with the listed causes above. In this case it is advised to check the egg shell quality to be sure that the cause is not a bad egg shell quality.


The navel area is vulnerable for infection and this can influence the post-hatch performance of the chicks. Depending on the navel issue, different incubation related parameters can be the cause. It is however important to eliminate external and technical factors before considering making changes to the incubation programme.

Petersime offers frontline support, basic incubation training, advanced hatchery management training and on-site hatchery performance audits to support our customers in every possible way.

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