The Ability of Young and Old Hens to Change Shell Deposition with Sudden Natural Drastic Changes in Egg Size

Abstract

Two experiments were conducted to determine if it is physiologically possible for the hen to deposit more shell on the egg than is currently deposited, and if so, what the hen's maximum ability is to change shell deposition as egg size is drastically increased or decreased under natural conditions. In Experiment 1, the first 10 eggs laid by each of 560 pullets were used. In Experiment 2, eggs were collected for 18 days from 560 hens approximately 14 months in lay. Egg weight, shell weight, and specific gravity were determined on all eggs in both experiments. Eggs from hens laying an occasional abnormally large egg (usually double yolked) or abnormally small egg were selected along with a normal size egg laid by the same individual hen on the adjoining day and various comparisons made.The results indicate that when a drastic decrease in egg size occurred in young or old hens, shell weight also decreased in about the same proportion resulting in no significant change in shell quality (specific gravity). When a drastic increase in egg size occurred in young and old hens, shell deposition increased but not enough to prevent a decline in shell quality.These results indicate that hens can significantly increase shell deposition with sudden drastic changes in egg size. The increase was approximately 7.5%. This suggests that it is possible for hens to deposit more shell on the egg than is currently being deposited if the proper stimulus is applied.