EXAMINATION OF THE POTENTIAL ROLE OF GAMMA-CARBOXYGLUTAMIC ACID IN EGGSHELL QUALITY

The outer portion of the outer shell membrane of hen eggs was removed, subjected to alkaline hydrolysis and analyzed for .gamma.-carboxyglutamic acid (Gla) via amino acid analysis. Although the presence of a ninhydrin positive substance was found in close proximity to the Gla reference peak, gas chromatographic-mass spectrophotometric analyses of this peak revealed that it was not Gla. Recently .gamma.-carboxyglutamic acid was found in the shell matrix. To determine whether the presence of Gla in the shell matrix is essential for the production of a strong shell, hens were fed a vitamin K antagonist and their eggs were evaluated for shell quality. Although prothrombin times were significantly increased, no significant changes occurred in the specific gravity measurements of eggs laid during the 14 days of treatment. This information strongly suggests that the carboxylation of glutamic acid is not an essential step in the formation of a strong eggshell.