Adaptation of dietary supplies to the daily variations of calcium and phosphorus requirements in the laying hen

Abstract

A laying hen which is offered a recognizable dietary calcium source (separate calcium feeding or SCF), consumes this calcium according to a discontinuous schedule in relationship with eggshell formation. This practice decreased bone mobilization and increased eggshell strength in 50 % of the trials. The effect is increased when environmental temperature is high. SCF also enables decrease in the dietary phosphorus level. More generally, the amount of deposited eggshell and blood phosphorus level are negatively related both in the long term and instantaneously. Consequently, the dietary available phosphorus level has to be limited at 0.28 % for an egg mass production equal to 60 g/d. Daily variations in dietary phosphorus seem to present some possible advantages : it must be as low as possible during the afternoon while calcium providing has to be of the highest level. Intermittent lighting programmes which desynchronize ovulation may also decrease the phosphorus requirements.