Observations on the Changes in Physical Characteristics that Influence Egg Shell Quality in Ten Strains of White Leghorns

Abstract

Egg weight, shell weight, and specific gravity (SG) were measured and percent shell and shell weight per unit surface area (SW/SA) were calculated for eggs laid over 5-day periods by hens from three 2-way and three 3-way strain crosses, three commercial strains, and a control strain. The measurements were taken when the hens were 165, 225, 277, 335, 390, 445, and, 490 days of age. Egg weight increased continuously between 165 and 490 days for all strains. Shell weight increased between 165 and 335 days, after which it remained nearly constant. Consequently, there was a concomitant decrease in percent shell and SW/SA. There were small decreases in SG between 165 and 490 days. Changes in egg shell weight were more variable for the commercial than the 2-way and 3-way strain crosses. The results indicate that egg size may be a factor influencing the shell quality of older hens.