There are many factors that affect the incubation of eggs, but here are five properties that you should look for when selecting eggs for incubation:

1. Fertility: This is the most important property, because without it, there is no chance of hatching. Fertility means that the egg has been fertilized by a male and contains a developing embryo. You can check for fertility by candling the egg, which means shining a light through it and looking for blood vessels or a dark spot.

2. Weight: The weight of the egg affects the size and health of the chick. Generally, heavier eggs produce larger and stronger chicks, but too heavy eggs may have lower hatchability due to reduced oxygen supply or shell quality. The optimal weight depends on the breed and type of poultry, but a good rule of thumb is to select eggs that are within 10% of the average weight for that breed.

3. Shell thickness and porosity: The shell of the egg protects the embryo from physical damage and microbial infection, but also allows gas exchange and moisture loss. The shell thickness and porosity depend on the age and nutrition of the hen, as well as the environmental conditions. Too thick or too thin shells can reduce hatchability by affecting the temperature, humidity and ventilation inside the egg. Ideally, you want eggs with uniform and smooth shells that have moderate porosity.

4. Shape index: The shape index of an egg is the ratio of its maximum breadth to its length, expressed as a percentage. For example, a perfectly spherical egg would have a shape index of 100%, while a very elongated egg would have a low shape index. The shape index affects how well the egg fits in the incubator and how evenly it is heated and turned. Eggs with extreme shape indices may have lower hatchability due to poor positioning of the embryo or difficulty in pipping. You should select eggs with a shape index between 73% and 79%, which is considered normal for most poultry.

5. Consistency of the contents: The consistency of the contents of an egg refers to how well the yolk and albumen (white) are held together by the chalazae (the twisted strands that anchor the yolk). The consistency affects how well the embryo can move and rotate inside the egg, which is important for its development and hatching. Eggs with watery or loose contents may have lower hatchability due to embryonic malformations or mortality. You should select eggs with firm and clear contents that do not slosh when gently shaken.

These are some of the properties that you should consider when selecting eggs for incubation, but remember that there are other factors that influence the success of hatching, such as temperature, humidity, ventilation, turning and sanitation. Happy hatching!