Effect of dietary levels of calcium on performance of pullets and layers, physical characteristics of the egg, and calcium and phosphorus in plasma and bone.

From 16 weeks old 432 chickens of a medium-heavy strain were given diets based on maize, soya bean oilmeal and barley with 1.5, 3.7 or 5.0% calcium and about 0.8% phosphorus. Diets supplied metabolizable energy 12.12, 11.35 or 10.96 MJ/kg. After a laying phase at 23 weeks old when they reached 50% production, chickens given 5.0% Ca weighed significantly less and tended to eat more than those given 1.5 or 3.7% Ca. Ca in plasma did not differ among groups but inorganic P was greater in those given 1.5% Ca than in others. During the laying period of 22 weeks egg production was greatest with 3.7% Ca. Feed intake, egg shell thickness, relative density of egg shell and proportion of shell increased with increasing Ca in the diet. Egg weight, albumen index and yolk index did not differ among groups. Tibial ash and breaking strength of tibia increased with increasing Ca in the diet. (Abstract retrieved from CAB Abstracts by CABI’s permission)