a) Why not a white Plymouth rock maternal stock?
A friend of mine told me that big companies use WPR.
Some white rocks have silver and recessive white and will work. Some white rocks do not have silver or are based on black with dominant white. These will not work. There are different ways to make white, many of those will not give a red sex link. There is no way to make a solid white bird just using silver, you need recessive white or dominant white to get a solid white bird. That makes any solid white bird problematic unless you know the genetics. The hatcheries know the genetics. You can try it with your white rocks, it may or may not work.
b) If we use a light sussex the tail of the final hybrid hen will be black.
If we use a riwmother, the tail of the final hybrid female will be white.
Is it true.
Interesting question. I doubt it will always be true, with either one it will depend some on the father. The Rhode Island White is another of those solid white birds that are problematic. I don’t know what the genetic make-up of the RIW is but several years back I got a bunch of RIR rooster over RIW hen sex linked cockerels from Meyer and they all had white tails. Here is what a few of them looked like.
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