The true ancestory of the American Silver Fox is not known for certain (except that all domestic rabbits descended from wild European rabbits). The breed was developed by Walter B. Garland of Canton, Ohio. In Bob Whitman's book, he writes that he believes that the Silver Fox originally came from a cross of the Champagne D' Argent and an American Blue. The Silver Fox breed was recognized in the US in 1929.
Reproduction and diet is the same as any other domestic breed, so you can find that information from sources at your library or on the internet.
Pam