Effects of Setting Eggs with Small Ends up on Hatchability and Chick Performance

Eggs are incubated in setter trays for most of the incubation period. Three days before hatch, the eggs are transferred to hatcher baskets, writes Pas Reform Hatchery Technologies.
calendar icon 18 July 2008
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In the setter trays, eggs are placed vertically with the air cell (large end) up, while the eggs lie horizontally during hatching.

In normal development, the embryo begins to turn to its position along the long axis of the egg on day 14. On day 18, the beak is turned to the air cell and covered by the right wing. In this position, the embryo can penetrate the inner cell membrane to gain access to the air in the air cell - after which, breathing starts.

This normal sequence of events is disturbed if the egg is placed with the air cell down and the small end up. In this scenario, the embryo still turns along the long axis of the egg with the head up but now, the head is positioned in the small end of the egg - away from the air cell. The embryo may die because the initiation of normal lung breathing is hampered or even prevented.

Hatchability of eggs placed with small end up is 12-30 per cent lower than in eggs set large end up. However, once hatched from an egg set small end up, the performance of chicks is no different from that of chicks hatched from eggs placed large end up. In the table below is a summary of data collected from commercial hatcheries. Over 3,600 eggs were candled from each flock. The percentage of eggs placed small end up varied between 0.29 and 3.4 per cent, irrespective of the shape of the eggs.

Flock Large end up Small end up


Hatchability (%)



Cull (%)



Grade-A chicks (%)




Hatchability (%)



Cull (%)



Grade-A chicks (%)




Hatchability (%)



Cull (%)



Grade-A chicks (%)



Reference: Bauer F., S.G. Tullet and H.R. Wilson, 1990. Effects of setting eggs small end up on hatchability and posthatching performance of broilers.


The incidence of eggs set upside-down is largely dictated by human error and not by the shape of the eggs. Great variation between trays in the number of eggs placed upside down was observed: some trays had none, while others had 10-12 eggs placed small end up.

Hatchability of eggs set small end up decreased by between 16.0 and 27.3 per cent. The frequency of non-viable chicks from eggs set small end up is higher but it varies between different batches of eggs. A hatchery loses 0.2 per cent of saleable chicks for each 1 per cent of fertile eggs placed with the small end up in a setter tray (Bauer et al., 1990).


Check each batch of eggs for the incidence of eggs placed small end up (upside down).

Register the number of eggs placed upside down on Pas Reform's Hatchery Recording Form number 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).

If the frequency of eggs placed upside down is unsatisfactory, investigate and remedy the reasons for misplacement of the eggs. If the eggs are routinely set in setter trays at the breeding farm, it is advisable to communicate the benefits (profit) of good placement and place responsibility for ensuring that eggs are place correctly with farm personnel. Breeder farm personnel should all be aware of the fact that the hatchery loses 0.2 per cent of saleable chicks for every 1 per cent of fertile eggs placed small end up in a setter tray.

For further information or advice, please contact the Pas Reform Academy.

May 2008

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