Most “ridged,” “sunburst,” “slab-sided,” soft-shelled, or double-shelled eggs are the result of eggs colliding in the shell gland region of the oviduct when an ovum (yolk) is released too soon after the previous one.
Postmortem examinations have demonstrated that two full-sized eggs can be found in the shell gland pouch. As the second egg comes in contact with the first, pressure is exerted, disrupting the pattern of mineralization. The first egg acquires a white band and chalky appearance, while the second egg is flattened on its contiguous surface (ie, slab-sided).
Other abnormal egg types may occur:
Pimpled or rough eggs may have been retained too long in the shell gland.
Blood spots result when a follicle vessel along the stigma ruptures as the ovum is being released.
Meat spots occur when a piece of follicle membrane or residual albumen from the previous day is incorporated into the developing egg.
Many abnormalities appear to have no specific cause; however, the incidence is much higher in hens subjected to stressful management conditions or rough handling (catching or vaccination) during production. A notable increase in the number of soft-shelled eggs is also common as a result of viral diseases such as infectious bronchitis Infectious Bronchitis , egg drop syndrome Egg Drop Syndrome 76 , Newcastle disease Newcastle Disease and Other ParamyxovirusInfections , avian pneumovirus Avian Metapneumovirus , and avian influenza Avian Influenza (see and photographs).
Occasionally, small eggs with no yolk form around a nidus of material (residual albumen) in the magnum of the oviduct. Small eggs with decreased albumen and eggs with defective shells may be the result of damage to the epithelium of the magnum or shell gland.