Eggs laid by the hens without mating the cock will not hatch out, as they are infertile without any germ inside to develop into a chick. Within 21 days a minute germ is transformed into a chick, by a rapid development and change within an egg. All eggs laid by a hen are not fit for hatching. Suitable eggs that could be hatched-out should be carefully selected on the following basis.
Fresh eggs collected from vigorous and well matured hens, 5- 7 days after mating and within 2 days of separating the cock will be fertile enough for hatching. Eggs collected immediately on letting in the cock for mating or long after the separation of the cock the egg may not be fertile.
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Egg size and shape
The size of the eggs used for hatching is important because the size of the chick hatched highly depends on the size of the egg. The eggs for setting should be neither too big nor too small, depending upon the breed. It is always desirable to select eggs of about 58 g each. Uniform sized and oval shaped eggs are good.
The egg shell should be of uniform thickness, texture and colour so that the warmth can uniformly spread during incubation. In case of white shelled eggs, all eggs for incubation should be free from tints. For brown coloured eggs medium and dark brown eggs: hatch better than the light brown eggs. When shell texture is poor due to deficiency of calcium or vitamin D, it results in low hatchability. All eggs should also be tested for cracked shells, as they should not be used for incubation.
Eggs should be fresh and not stale, collected as early as possible after laying, at any rate within a week of laying. Very fresh eggs just laid on the day of setting may not be advisable to be set unless they attain the room temperature before setting. Eggs of 2- 4 days old are excellent.
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Eggs with any deformity such as ridges, encrustations, projections, depressions, cracks or stains should not be selected. Very thin shells may break during turning and will not retain uniform temperature for embryo to develop. If the shell is very thick, there will be difficulty for the chick to chip it with its tender beak and come out.
Soiled eggs should not be washed in water before setting, as washing with water opens up the pores and this interferes with the hatching results. If the dirt is not excessive, it should be removed with a knife. Highly soiled eggs should not be used.
Eggs collected for setting should be kept in a dry, cool and airy place in order to get the best results. In hot weather, eggs should not be kept for more than 3 days and in winter or in hilly areas it can be kept up to 10 days.
As eggs absorb odour very easily, it is not good to store them near smelly substances like onion, garlic, kerosene etc. Eggs should be stored in a cool place with the broad ends up. Eggs shaken very much during transport will not be good for hatching.