Requirement of calcium for commercial broilers and white leghorn layers at low dietary phosphorus levels

Abstract Two experiments were conducted to study the requirements of calcium (Ca) for commercial broilers (1–35 day of age) and White Leghorn (WL) layers (196–336 day of age) at a constant levels of phosphorus (P) recommended in the literature. In the first experiment, four levels of Ca (7, 8, 9 and 10 g kg −1 ) were tested in a maize–soya bean meal and de-oiled rice bran based diets at a constant level of non-phytin phosphorus (NPP) (3.5 g kg −1 ) with commercial broiler housed in stainless steel battery brooders. The experimental diets were fed ad libitum to 16 replicate groups of six broilers (three males and three female) in each replicate. Level of Ca in the diet significantly influenced the body weight gain ( P ≤0.05), serum Ca level, tibia ash contents ( P ≤0.01) and retention ( P ≤0.05) of Ca and P. The level of Ca in diet did not affect the feed intake, feed per gain, leg abnormality score, net Ca retention and serum P content. The predicted requirements of Ca for maximum weight gain, serum Ca content and tibia ash content were 7.56, 9.72 and 9.83 g kg −1 diet, respectively. In the second experiment, six levels of Ca (32.5, 35, 37.5, 40, 42.5 and 45 g kg −1 ) were tested in a maize–soya bean meal–sunflower–de-oiled rice bran based diets containing a constant level of NPP (2.8 g kg −1 ) with layers. The experimental diets were fed ad libitum to six replicate groups (six layers in each replicate) housed in individual cages. Hen day egg production, feed intake, feed egg per mass, shell quality (shell thickness and shell weight), tibia ash content, tibia breaking strength and concentration of Ca and P in serum were not influenced by the level of Ca in the diet. The retention of Ca and P in the broiler experiment and the activity of serum alkaline phosphatase in the layer experiment were inversely related to the level of Ca in the diet. Based on the results, it can be concluded that the requirements of Ca for commercial broilers (1–35 day of age) and WL layers (196–336 day of age) are 7.56 and 32.5 g kg −1 diet, respectively. However, considering the trend seen with serum Ca concentration and tibia ash content in broilers and the activity of serum alkaline phosphatase in layers, it may be desirable to provide 8 and 35 g Ca kg −1 in broiler and layer diets, respectively.