Abstract
Abstract A 3 × 3 factorial experiment with 324 laying hens was conducted for 280 days to examine the effect of calcium and available phosphorus on biological responses associated with egg production. Calcium levels were 2.50, 3.75, and 5.00% and available phosphorus levels were .35, .50, and .65%. The data were analyzed quantitatively using response surface methodology. Results showed that within the range of the experimental design, there were no significant effects of the two minerals on hen-day egg production, final body weight, or average egg weight. A trend was shown for improvement in feed conversion at the 2.5 and 3.75% calcium as the available phosphorus percent was reduced. This trend was not evident at the 5% calcium level. Cumulative mortality was related to low dietary levels of calcium. Eggshell percentage was significantly affected by calcium and available phosphorus levels. A second order equation was found to describe the mineral and percent eggshell relationship with an R2 value of .77. Optimal levels of calcium and available phosphorus for the percent eggshell were calculated to be 4.73 and .48, respectively. A confidence area and interval were described for the predicted optimal response. The high calcium and available phosphorus were postulated to be associated with the strain of hen used in the experiment.
Published Version
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