During the formation of

, the main pigment affecting the color of eggshell is protoporphyrin, which is synthesized by the eggshell gland of hens. These pigments are deposited on the outer layer of the eggshell and the membrane on the shell to form the egg color we see. Therefore, the difference in pigment secretion is the real reason for different colors of eggs. The ability of

and

to synthesize protoporphyrin is determined by genetic factors, so the eggshell color is mainly affected by genetic factors. For the same hen, the eggshell color is relatively fixed. If riboflavin and β – carotene are added to chicken feed, the color of egg yolk will become darker, but the eggshell may not. Because of the individual differences in the genetic ability of the hens to synthesize protoporphyrin, even the eggshell color of the same breed is different. In particular, commercial chickens are usually crossed by several genetic lines, and the difference is more obvious. The weight of

and

eggs increased with the age of hens, but the secretion of pigment on the shell membrane was fixed and did not change with age. Therefore, when the hen’s egg weight increases with age, the limited pigment will be distributed on the eggshell with expanded surface area, resulting in the eggshell color becoming lighter. The color of

and

eggshell has nothing to do with the formation of the protein and yolk, but the nutrition we need is basically from protein and yolk. Therefore, the selection of eggs or do not pay too much attention to the color of the eggshell, color alone is difficult to determine which kind of egg is more nutritious. Therefore, in the choice of eggs, or fresh is better.

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