Do hairline-cracked eggs influence hatchability and chick performance? - By Pas-Reform - In general, good quality eggs are selected and placed for incubation. This means that only clean eggs with shell intact should be placed on the setter trays.

Background

Dirty or floor eggs and eggs with visible cracks are removed and not placed. Eggs with hairline cracks might often not be recognised and will, consequently, be placed in the setter trays and incubated.

In cracked eggs, the shell is broken and the underlying membrane is ruptured - leading to dehydration and the death of the embryo. However eggs with undamaged membranes but broken shells are defined as having hairline cracks - and these are often placed because unless candled, they look like good quality eggs.

A research group from the University of Alberta has recently analysed the weight loss, embryonic mortality and hatchability of eggs with hairline cracks, with the following findings:

Eggs from five commercial flocks of various strains were candled and an equal number of hairline-cracked and normal eggs were incubated for 21 days. Eggs were identified as having a hairline crack if the crack was visible by candling, but not apparent when examined normally. The results are summarised in the table.

Conclusions

1. Setting eggs with hairline-cracks significantly reduces hatchability.

2. Chicks hatched from hairline-cracked eggs show a higher incidence of mortality during a 14 day growing period.

3. Egg weight loss during the setting period increases significantly in hairline-cracked eggs; consequently chicks hatched from hairline-cracked eggs are smaller. This, however, had no effect on day 14 weight.

4. Compared to good quality eggs, a significantly higher incidence of contaminated and broken eggs was found after incubation of hairline-cracked eggs.

Advice

1. Hairline-cracked eggs should not be incubated.

2. candle egg samples from batches transported to the hatchery on a regular basis.

3. Register the number of eggs with hairline-cracks on Pas Reform’s Hatchery Recording Form no. 2C (to receive your free copy of Pas Reform’s Hatchery Recording Forms, please complete and return the order form in the Library document Incubation Guide on www.pasreform.com).

4. If the frequency of hairline-cracked eggs is unsatisfactory, investigate and eliminate possible causes.

5. Try to avoid the use of plastic trays with sharp edges for the transportation of eggs, as these are likely to be a major cause of hairline-cracks.

Source: Pas Reform - April 2006