Abstract
Two experiments were conducted to determine calcium and phosphorus reqirements for White Leghorn growing pullets of 10 or 11-21 weeks of age. Pullets hatched in February and October were used in the first and second experiments, respectively. Basal diet was primarily composed of yellow corn and soybean meal without any animal protein source, containing 0.45% total phosphorus (all plant phosphorus) and 0.2% calcium. Six experimental diets of 0.45 and 0.60% phosphorus (0.15% inorganic phosphorus) levels, with 0.5, 0.75 and 1.0% calcium levels to each phosphorus levels, were fed in each experiment. After 21 weeks of age, practical laying ration (0.75% phosphorus and 2.75% calcium) was fed to all the pullets.
It was found that dietary calcium and phosphorus levels during growth in 10-21 weeks of age in these experiments, did not significantly affect body weight gain, feed efficiency, tibia ash, sexual maturity and egg production.
It was concluded that calcium and phosphorus requirements for White Leghorn growing pullets of 10-21 weeks of age were 0.5 and 0.45%, respectively. These were much lower than what was recommended by National Research Council. It appears that the whole amount of dietary phosphorus to the level of requirement (0.45%) can be supplied with plant phosphorus.
