THE INFLUENCE OF VARIOUS CALCIUM AND PHOSPHORUS LEVELS ON TIBIA STRENGTH AND EGGSHELL QUALITY OF PULLETS DURING PEAK PRODUCTION

One thousand and eighty DeKalb XL pullets were randomly allocated to nine treatments and arranged in a 3 x 3 factorial to determine the effects of three levels of dietary calcium (2.75, 3.75, and 4.25%) and three levels of dietary available phosphorus (.30, .40, and .50%) on eggshell quality and tibia weight, tibia breaking strength, tibia ash, and bone mineral content of pullets during peak production. Feed consumption increased as dietary calcium or phosphorus increased. Increasing dietary calcium caused a significant linear increase in egg specific gravity, but dietary phosphorus had no significant effect on egg specific gravity. Calcium and phosphorus levels did not significantly affect egg production, body weight, plasma chloride, or phosphorus. Ionized calcium increased significantly as dietary calcium increased. Tibia breaking strength, tibia weight, tibia ash, and bone mineral content increased significantly with increasing dietary calcium. Dietary phosphorus had no significant effect on these parameters. However, when 2.75% calcium was fed, reducing dietary phosphorus significantly decreased tibia weight, tibia ash, and bone mineral content.