I'll be interested to hear someone chime in! My thought was that genetics controlled egg color (so it wouldn't change regardless of diet), but you could change yolk color by adding more greens to their diet.
you will have to let us know what you read. Here's what I have heard. One of the reasons that home eggs are richer looking and tasting than store eggs is that the greens that the chickens at home forage contribute the rich orangey color to the yolks. Commercial producers started putting marigold petals into feed to darken the yolk color. (some commercial feeds have marigold listed on the ingredients). Also, if the chicken eats acorns, the yolks will take on a greenish color.
Regarding shells....the chicken is supposed to lay the same color shell always. One of mine didn't get the memo and she lays various shades of light brown and sometimes speckled eggs. I get precolored eggs from a Barred Plymouth Rock--- however, I am beginning to suspect she has additional genetics in her ancestry.
No it specifically said egg shell shades like adding plants with more iron, and other naturally occurring metals in the plant makes the shell darker, greener, bluer and so on. Then combine that with the birds that produce a like shade for even more enhancement. Your comits is what I thought as well. I read all kinds of stuff on the web, books and as you know some is good and some not. The old sayings always confirm and re-confirm what hear and nowadays what you see... Still was interesting and may even work very slight but not worth the time for what may not work at all. Thanks
There could be something to the iron content affecting shell color.
I've read that the coloring agent that produces brown eggs is created from breakdown products of the hen's hemoglobin. An important part of which is iron. It may be that supplying additional iron could boost the amount of brown coloring agent in the shells.
Whether it actually does do this or not I cannot say. I am sure though that there is a definite upper limit to whatever the affect may be.
Edited to correct the above. It seems the blue coloring agent is a breakdown product of the hen's bile.
Egg shell color is genetic
Blue X Blue = Blue
Blue X White (eg, Leghorn) = Blue to Light Blue
Blue X Brown (eg, RIR) = Green
Blue X Dark Brown (eg, Maran) = Olive Brown
Genetics of eggshell color:
Brown eggshell color is a complex trait and as many as 13 genes have been proposed to account for the range in eggshell color. The white eggshell color is due to an absence of blue and brown, and perhaps some modifying factors (genes), since there are different shades of white. The blue eggshell gene, O, expresses if it is present which is why it is considered to be dominant. The gene symbol for the recessive, wild-type gene is o or o+. My understanding at present is that the locations of the brown eggshell genes are not known and it is not known how many brown modifying genes there are or where they are in relationship to the genes of known locations. Brown may itself be just an array of white modifiers. There is a recessive sex-linked gene, pr, that inhibits the expression of brown eggshell genes and can be used to help remove the brown tint from white eggs, for example.
The brown pigment, ooporphyrin, is deposited primarily on the outside of the eggshell and is a chemical compound resulting from hemoglobin metabolism. In fact, much of the brown pigment can be buffed off with a common kitchen (plastic) scrubbing sponge and warm soapy water. The blue eggshell pigment, oocyanin, is a byproduct of bile formation and is present throughout the eggshell.
The eggshell color genes interact in the following way. The effect of the blue gene is dominant over white. The effect of the brown gene is dominant over white. When blue and brown genes are both present, both genes contribute to the eggshell color making the eggs appear green. In this case, the inside surface of the eggshell will be significantly less green and more blue than the outside surface, which is where most of the brown pigment is.
Since the blue and brown eggshell color genes should be at different locations, we need at least two pairs of genes to describe the genotypes of the blue, white, green and brown layers. For the purposes of this discussion, I use the fictitious symbol, Br, to indicate a brown eggshell color gene. I represent the complementary recessive gene that takes the place of Br when it is absent as "br" (lack of brown gene). We can represent the genotype of a blue eggshell layer as (O, O) with (br, br). Blue and white genes, (O, o) with (br, br) also yields a blue egg, but perhaps a lighter blue. The pair of eggshell color genes, (O, O) with (Br, Br), are the genes for producing a green egg, (o, o) with (Br, Br) produces a brown egg and (o, o) with (br, br) yields a white egg. Females having one blue gene and one or more brown genes will lay eggs having a greenish color. My personal experience with eggshell color makes me believe that this genetics picture of eggshell color is oversimplified (there are certainly more than one gene for brown eggshell color. In order to account for the wide range of shades of brown eggs we see in our Sil-Go-Link line, there must be a relatively large number of eggshell color modifying genes that are not yet known. Most people accept a rule of thumb to the effect that a daughter will lay eggs that are a color between that of the parent lines.
To explore the genetics of eggshell color, lets cross a green egg layer (faux-Araucana or Easter Egg Chicken) with a white egg layer (Leghorn). Here as before, I will use the fictitous symbol "Br" to represent brown eggshell genes. The genes of the green egg layer are (O, O) with (Br, Br) assuming the locations of the blue and brown genes are not the same. The Leghorn is (o, o) with (br, br) for eggshell color (white). In this example, the daughters will all have one gene for blue eggshell color and one gene for brown. They will all be green egg layers! My personal experience with eggshell color genetics leads me to believe it is more complex than this. There certainly must be a number of brown eggshell genes and once you have them, it is difficult to breed them out completely.