Fresh or mature?   

Fresh eggs.

What eggs is it better to lay under a broody hen: fresh or mature?
Of course, it is better to lay fresh eggs. If they have to be stored for the incubation, special premises should be assigned and in it the temperature of 8-12°Ñ and the 75-80% humidity should be provided. In the eggs storage there should be good ventilation so that the air in it is clear, without foreign smells.

Eggs storage.

Hen, turkey, guinea fowl and small duck eggs are stored in the vertical position (with the blunt end upwards), and big duck and goose ones - in the horizontal position.
Hen eggs can be stored not more than for 5-6 days, duck and turkey eggs - not more than 7-8 days, guinea fowl eggs - not more than 8-10 days.
When it is necessary to store eggs for longer periods, eggs are heated. This procedure should be performed on the 2nd-4th day from the moment of their having been laid. Eggs are stored into trays and for 5 hours are heated in the incubator at the temperature of 37.5°Ñ and the 70% humidity. After that they are carried to the eggs storage and stored up to 15 days.