People of my generation (I am 75) can remember when hens鈥� eggs used to have a rounded end and a pointy end. Now the ends seem much more alike. Have eggs changed over the years, and if so, why?
鈥� Most eggs still have a round end and a pointy end 鈥� indeed, a quick survey of eggs from battery hens in my local supermarket revealed 100 per cent normal eggs, although just what is egg-shaped is open to debate. Any spherical or near-spherical eggs are most likely a result of severe inbreeding.
The majority of commercial egg-laying chickens are ISA Brown hens 鈥� ISA standing for Institut de S茅lection Animale 鈥� which have been specifically bred for maximum egg production. These birds are now found across the world and frequently exhibit genetic faults previously found only in obscure textbooks.
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My purebred Wyandotte chickens lay 鈥渘ormal-shaped鈥� eggs, with each hen laying a shape that is distinctly her own. The eggs get bigger during the laying period (between three and five days is normal) as the thickness of the shell decreases and its radius of curvature increases. This affects shell strength and means that eggs laid later are fatter, though never spherical.
After the laying period, the hen will take a break of up to two days and begin again. Battery fowl kept in heated environments with controlled lighting will have a laying period of up to three weeks before taking a short break.
Eggs pass along the oviduct 鈥減ointy鈥� end first. If the hen is not frightened or interrupted, it will rotate the egg horizontally in the cloaca just before laying so that the egg is expelled round end first. If the bird is disturbed, the egg will be forced through pointy end first. The egg is laid with a soft shell that hardens rapidly in contact with the air.
Nina Dougall, Malmsbury, Victoria, Australia
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