Effect of Dietary Protein on Selected Properties of the Egg

The response of laying hens fed isocaloric rations with protein contents of 12, 14, 16 or 18 % was studied. The 12% ration was calculated to be deficient in essential amino acids methionine and cystine. Production responses (decrease in egg production and egg size, and overconsumption of energy) verified the deficiency. Ash and total solids content of whites and whole eggs did not vary with the level of dietary protein; but total nitrogen in whole egg and albumen was a function of the dietary protein intake and increased as the level of protein increased in the diet. Sponge cake volume appeared to improve with eggs from the rations of higher levels of protein. The volume of egg white formed per egg by hens receiving a suboptimal protein diet was less than that of eggs from hens receiving an adequate amount of dietary protein. Egg white proteins were separated by a method utilizing polyacrylamide disc gel electrophoresis. The technique, using 14% polyacrylamide gel, yielded separation comparable to starch gel patterns of egg white. Fractions faster than ovalbumin and slower than conalbumin were observed but their identification will depend upon further work using purified protein fractions. With the ease of preparation and high resolution, disc electrophoresis may be an applicable tool to further identify and measure minor egg proteins.