Dietary calcium restriotion is studied as a method of
controlling egg production. Attempts have been made to delay the
onset of egg production in the fowl by feeding pre-laying diets
deficient in calcium. Calcium restriction had no apparent effect
on sexual development and did not delay the time· of first
Low calcium diets were used at a later date to halt egg
production firstly just after peak production and secondly towards
the end of the first laying year. Egg production was depressed
markedly but never completely ceased, and remained at a low level
until calcium restrictions were lifted whereupon a rapid rise
returned egg production to levels comparable to egg production
rates of non calcium restricted control hens.
Comparisons between egg production, egg weight, shell weight
and a measure of shell quality (shell weight per unit surface area
of egg) revealed trends towards improved shell production and shell
quality following calcium restriction but little else. There was
only a small number of significant differences. Egg production
pauses induced by low dietary calcium were thought to be
unsatisfactory as substitutes for force moulting.
Calcium restriction caused declines in food consumption and
body weight. While food consumption returned to levels equivalent
to food consumption of non calcium restricted hens after calcium
restriction, body weight in general did not.
Calculations of the calcium loss from the body of calcium
restricted hens via egg·shell production show that extremely severe
depletion occurs unless egg prvduction is stopped or at least egg
shell production is stopped. Such depletion of calcium has greatest
effects on the skeleton and damage to the bones, particularly of
the legs, may result. This is a condition which may predispose to a
paralytic condition characteristic of extreme calcium deficiency.