Thursday, April 29, 2010

About Eggs

Factoids (courtesy of Harold McGee's "On Food And Cooking"):
  • Chickens are "indeterminate" egg-layers, which means instead of laying a fixed number of eggs a fixed number of times per year, they keep on laying each day until they accumulate a certain number. If a predator, such as a human, takes one of the eggs before she finishes she will replace it before stopping. If the predator keeps taking the eggs she will never stop.
  • An animal's "reproductive effort" is the fraction of her body weight which she deposits daily in her future offspring. A hen's reproductive effort is 100x that of a human.
    • An egg weighs 3% of a typical hen's weight, and she may lay an egg almost every day.
      • Imagine a human woman having a four-pound baby every day!
    • An industrial hen may produce eight times her body weight in eggs over the course of her year-long life.
    • A hen expends 25% of her daily calorie budget on egg-making. (Ducks expand half their energy on egg-laying!)
  • Hens have only one ovary.
  • Hens store sperm inside their oviducts. After the germ cell has accumulated enough yolk from the fats and proteins in a hen's liver, but before the egg white is added or the shell is formed, if the hen has mated recently some of the sperm will fuse with (fertilize) the germ. Either way the egg will still get laid.
  • An eggshell has about 10,000 little holes, concentrated at the blunt end, to let air into the egg while the embryo is developing. All these holes put together would be about as wide as the head of a pin (2 mm).
  • Inside of an egg yolk you can see a flat little white disc attached to ropy white things that look (sorry!) kind of like boogers. The white disc is the actual germ cell, whether fertilized or unfertilized, i.e. the chicken embryo. The ropy white things are designed to keep the embryo from smashing itself into the walls of the shell.
    • Good news! This means that you don't have to be queasy about eating unfertilized chicken embryos, or feel nauseous when you think about the texture of the yolk. That's just a bunch of fats and proteins from the mama chicken's liver. Only the little disc ever had any chance of becoming a chicken, even if it had been fertilized.
    • By eating the yolk you are, however, stealing candy from a baby. Unfertilized baby chicken, that is.
  • Modern industrial techniques transform feed into eggs with better than 33% efficiency, and feed into chicken meat at better than 50% efficiency. That is, you can produce a pound of eggs from less than three pounds of feed, and a pound of (broiler) chicken from less than two.
  • Egg color is totally unrelated to nutritional value or taste and is determined by the protein composition of the cuticle, which it the outermost layer (designed to slow water loss and block the entry of bacteria through the pores, at least initially).
    • Rhode Island Reds lay brown eggs.
    • Chinese Cochins lay eggs with yellow dots.
    • Chilean Araucanas lay blue eggs.
    • The cross between a Chilean Araucana and a Rhode Island Red lays green eggs.
Be pretty if you are,
Be witty if you can,
But be cheerful if it kills you.
If you're so evil, eat this kitten!

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