All my eggs over 14g are double yoke, I get 5 eggs a day ,the rest are 10 to 12g . They are on starter feed, Will be 7wk.'s old Sunday . They are Texas a&m coturnix. I'm knot keeping any wright now. Their off the lights now.Going to change over to layer Feb 1st.
double yoke eggs
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There are several threads on the BYC incubating forums about hatching double-yolkers. They do produce twins, but most often they're not able to hatch successfully (with some notable exceptions). In the event that one baby dies along the way inside the egg, the other would die also, as it wouldn't be able to process the excess waste and bacteria produced by its dead companion. Likewise, in the event of only one yolk fertilized, I'd think the second yolk would eventually go putrid and kill the other.
Do a quick search for "double yolker incubation" and see what you turn up. :)