"Two experiments, which included three incubators, were carried out to investigate the effects of egg weight and position relative to incubator (setter) fan on embryonic mortality, second quality chicks and fertile hatchability of broiler eggs.

Three egg weight groups termed 'small' (approximately 62.4g), 'average' (approximately 65.4g), and 'large' (approximately 68.9g) were set in either the incubator trolley most distant from the fan (FAR) or in the incubator trolley nearest to the fan (NEAR) as would be the case during single-stage operation in this type of incubator," researchers in Ankara report.

"Fertile hatchability decreased in the large egg weight group due to increased percentage late embryonic mortality in experiment 1, and both percentage early and late embryonic mortality in experiment 2.

Percentage late embryonic mortality and second quality chicks increased and percentage fertile hatchability decreased for eggs in the FAR position in experiment 1 only.

A significant interaction of incubator position x egg weight group for late embryonic mortality, second quality chicks, and fertile hatchability was found in experiment 1, but only late embryonic mortality was so affected in experiment 2.

Experiment 2 was conducted so that eggshell temperatures could be measured.

The researchers concluded, "Large eggs in the FAR position at transfer time (E 18) exhibited significantly higher eggshell temperatures than did the other groups probably because air velocity or air distribution was modified in the FAR position of the incubator and large eggs were most negatively influenced in the trolley in this position."

Reference:
Elibol O. et al., 2008. Effect of egg weight and position relative to incubator fan on broiler hatchability and chick quality. Poultry Science, 2008. 87(9):1913-1918.