Estimation of Shell Weight and Shell Thickness from Egg Specific Gravity and Egg Weight
1982; Elsevier BV; Volume: 61; Issue: 10 Linguagem: Inglês
10.3382/ps.0611991
ISSN1525-3171
AutoresJON O. NORDSTROM, L.E. OUSTERHOUT,
Tópico(s)Plant Reproductive Biology
ResumoEgg weight (EW), egg specific gravity (SG), shell thickness (ST), and shell weight (SW) were determined individually for 1853 eggs ranging in weight from 41 to 70 g. The eggs were laid by three groups of Single Comb White Leghorn (H&N Nick Chick) laying hens, with at least 200 hens per group, ranging in age from 24 to 54 weeks of age. One group of hens, while they were 50 to 54 weeks of age, laid 62% of the eggs used. All hens were fed a laying ration that contained 16% protein, 3.25% calcium, and .53% phosphorus. Egg specific gravity was measured using the flotation method with the different solutions being .002 specific gravity units apart. Shell weight (mg) per square centimeter egg surface area (SWUSA) and percent shell (%S) were calculated for all eggs. Egg surface area was calculated from the egg weight (Carter, 1975). Multiple and simple linear regression analysis yielded the following equations: ST (mm × 100) = 11.056 + .4349 × SG + .2112 × EW (r2 = .767); SW (g) = −5.972 + .06586 × SG + .09906 × EW (r2 = .890); SWUSA (mg/cm2) = 30.670 + .9565 × SG + .4571 × EW (r2 = .821); %S = −.3773 + .1140 × SG (r2 = .875); where SG is (actual SG-1.0) × 1000 and EW is in grams. The ST, SW, and SWUSA were predicted more accurately with both SG and EW as independent variables than by using either single variable. Percent S was predicted as well by the use of SG as a single independent variable. Egg weight influences interpretation of specific gravity and percent shell data, because specific gravity and percent shell decreased as egg weight increased (.00053 and .054 units, respectively, for each 1 g increase in egg weight) for eggs differing in weight but with the same shell thickness.
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