Hatchability of Chicken Eggs as Affected by Dietary Phosphorus and Calcium

Two experiments with caged egg-type hens and one experiment with broiler breeder hens on litter floors were conducted to determine interactions between dietary calcium and phosphorus as related to hatchability and other production characteristics. Reductions in hatchability of eggs from caged layers caused by suboptimal levels of inorganic phosphorus were partially offset by elevation of the dietary calcium. When phosphorus in the diet of caged layers was supplied entirely from plant sources, elevation of dietary calcium resulted in decreased hatchability and egg production. Hatchability of fertile eggs from broiler breeder hens on litter floors was not significantly affected by dietary calcium levels of 2.25 to 3.50%, or by total phosphorus levels of .31 to 1.42%. Egg production was improved by supplementation of the diet with inorganic phosphorus up to .41% total phosphorus, but it was depressed by further supplementation. Egg specific gravity decreased with increased phosphorus levels and was significantly depressed by high dietary phosphorus (1.42%). Recycling of phosphorus by coprophagy may be a factor affecting dietary phosphorus requirements of hens in litter floor pens.