Egg Quality. 1. Shell Strength of Eggs from Five Commercial Strains of White Leghorn Hens During Their First Laying Cycle

Abstract

Eggs were collected 18 times from five strains of commercial White Leghorn hens between 197 and 484 days of age. Egg weight, specific gravity, nondestructive deformation, and quasistatic compression breaking strength were measured on all eggs. Shell weight, percent shell, and shell weight per unit surface area were available for eggs collected between 372 and 484 days of age. Shell thickness was measured at 421, 449, and 477 days of age. Age and strain (P<.01) influenced all the variables except shell thickness, which was affected only by strain (P<.05). Egg weight and deformation increased and specific gravity and compression breaking strength decreased over the experimental period. Shell weight, percent shell, and shell weight per unit surface area decreased slightly between 372 and 484 days. The variability, expressed as the standard deviation of an observation, remained relatively constant for specific gravity, egg weight, shell weight, percent shell, and shell weight per unit surface area. It increased for deformation between 197 and 484 days. The variability of compression breaking strength was not constant over the experimental period, but neither did it exhibit any simple trend. There were few interactions: strains of hens which had the highest shell quality at 197 days also had the highest at 484 days.