The colour giving substances in the eggshell are ooporphyrins and oocyanin. The ooporphyrins, derivatives of haemoglobin in the blood give brown colour and oocyanin, a product of bile formation gives bluish green colour to the shell. The eggshell devoid of these pigments is white in colour. Combination of these two substances in different proportion gives different shades of colour to the eggshell.The genes determining shell colour are entirely different from those responsible for feather colour. Therefore the shell colour in chicken has no relationship with the plumage colour.
The colour of the shell is characteristic to breeds. Breeds like Leghorn, Minorca and Andalusian lay white eggs; while, Rhode Island Red, New Hampshire, Cornish and Plymouth Rock are the few breeds that lay brown eggs. Irrespective of the plumage colour, both brown and white varieties of Leghorns lay white coloured eggs. Similarly, Cornish, be it a red or white variety lays only brown coloured eggs. A cross between a white egg breed and a brown egg breed will produce tinted brown eggs. In general, the breeds of chicken coming under Mediterranean class lay white-shelled eggs and almost all the breeds of other classes lay brown eggs. Araucana, an American breed, is the only chicken breed that lays blue-shelled eggs. Contrary to the general perception, the shell colour does not have any influence on the nutrient content of the eggs. On weight-to-weight basis the nutrient content of the eggs irrespective of their shell colour is similar.
Source: thehindu.com
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The colour of the shell is characteristic to breeds. Breeds like Leghorn, Minorca and Andalusian lay white eggs; while, Rhode Island Red, New Hampshire, Cornish and Plymouth Rock are the few breeds that lay brown eggs. Irrespective of the plumage colour, both brown and white varieties of Leghorns lay white coloured eggs. Similarly, Cornish, be it a red or white variety lays only brown coloured eggs. A cross between a white egg breed and a brown egg breed will produce tinted brown eggs. In general, the breeds of chicken coming under Mediterranean class lay white-shelled eggs and almost all the breeds of other classes lay brown eggs. Araucana, an American breed, is the only chicken breed that lays blue-shelled eggs. Contrary to the general perception, the shell colour does not have any influence on the nutrient content of the eggs. On weight-to-weight basis the nutrient content of the eggs irrespective of their shell colour is similar.
Source: thehindu.com
