Dietary calcium levels in pre-lay and lay diets in Leghorn pullets.
Four experiments over a period of four years with 1350 first-year pullets were designed to determine the influence of the calcium and phosphorus levels in the pre-lay diets on the growing birds and on their subsequent performance. Several dietary calcium levels in the lay period were studied, as well as the interaction between the pre-lay and lay diets. During the growing phase the pullets fed 3.0% calcium and 0.4% phosphorus had significantly (P less than 0.05) lower body weight at 20 weeks of age than thep ulletsin the other pre-lay treatments. Feed consumption and feed efficiency were also adversely affected by this treatment, and sexual maturity was significantly (P less than 0.05) delayed. Early lay mortality from this treatment was evident. On the basis of egg production, egg weight, shell deformation and percent poorly shelled eggs (PSE) at point-of-lay, the pre-lay diets did not influence lay performance nor was there an interaction between any combination of pullet and lay diets. As the calcium levels of the lay diets increased, egg production, feed consumption and shell rigidity increased. The 1.5% calcium level did not maintain bone mineralization as compared to the 3.0 and 4.5% calcium levels. It was noted that shell quality on the basis of PSE and deformation does not begin to deteriorate immediately after the onset of production. In fact there is a short period of time where the egg shells improve and then there is a gradual decline in shell rigidity. The layers fed the lay diet containing 1.5% calcium produced eggs weighing an average of 57.4 g. This was significantly (P less than 0.05) lower than the eggs of the 2.3, 3.0 or 4.5% calcium fed groups which produced eggs weighing 59.1, 58.6 and 59.4 g. respectively.