Page 22 - ALG Issue 1 2022
P. 22

Why are hen eggs different colours?
According to Michigan State University Extension, egg colour is determined
by the genetics of the hens. The breed of the hen will indicate what colour eggs she will produce. For example, Leghorn chickens lay white eggs
while Orpingtons lay brown eggs and Araucanas produce blue eggs. An olive egger, a chicken that lays olive green eggs, is the product of a cross between a hen and rooster that are from a brown egg and a blue egg laying breed. An interesting tip is to look at the chicken’s ear lobes; typically, those with white ear lobes produce white eggs.
All eggs start out white in colour; those that are laid in shades other than white have pigments deposited on them as the eggs travel through the hen’s oviduct. The journey through the chicken’s oviduct takes approximately
26 hours. The shell takes roughly 20 hours to be complete. Araucana birds have the pigment oocyanin deposited on the egg as it travels through the oviduct. This pigment is a by-product of bile production and permeates the eggshell resulting in the interior and exterior of the egg being the same blue colour. Chickens that lay brown tinted eggs deposit the pigment protoporphyrin on the eggs late in the process of forming the shell; this pigment is produced by
the breakdown of red blood cells. The pigment therefore does not penetrate the interior of the egg, but tints only the surface of the egg, which is why brown eggs are white on the interior. In the case of an olive egger, a brown pigment overlays a blue eggshell resulting in
a green egg. The darker the brown pigment the more olive colour of the resulting egg. The egg colour does not signify any difference in the quality of the egg.
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