A Method for Estimating Shell Weight and Correcting Specific Gravity for Egg Weight in Eggshell Quality Studies

Abstract

Two formulas were derived from definitions of egg density (ED) or egg specific gravity (ESG) or both. The formulas can be used for estimating ESG or shell weight (SW) when the other was not measured. The ESG formula can also be used to correct ESG for differences in egg weight (EW). This correction in ESG can be used when analyzing data from any experiment where differences exist in EW among treatments. In many reports from the literature, treatment differences for shell quality were found to be minimal when adjusted for EW. The formulas developed were used for estimating SW plus membrane and ESG for seven strains of hens fed six levels of calcium. These values were then correlated with measured values. The strains times calcium interaction was not significant. For measured SW versus calculated SW, the respective correlation coefficients were .979, .954, .974, .959, .965, .969, and .932 for the HyLine W36, DeKalb XL, Shaver, DeKalb DK, HyLine W77, Babcock Brown, and Hisex Brown Strains and were .923, .946, .973, .968, .963, and .954 for the respective calcium levels of 1.75, 2.0, 2.5, 3.0, 3.5, and 4.0%. The calculated ESG and measured ESG were highly correlated. These data indicate that ESG and EW can be used to obtain an excellent estimate for SW.