Since guinea pigs do well for maintaining a food forest floor how should I raise them so they put on weight quickly?
Think of a herd of guinea pigs for a few meals a year, and selling for pets.
When I visited Peru, EVERY house had a guinea pig pen in the back yard. Peru doesn't prep food like north Americans do, so there was a lot of husks, stems, trimmings, peelings. These went to the guinea pigs.
They were either used by the household, or sold to street vendors who would sell barbecued GP on the street. In 1969 you could get one for about 20 sols (65 cents) One time I got one that had lived it's life eating fish offal. Texture like chicken. Taste like tuna.
Anyway: A guinea pig let loose in your forest is going to be doggy dinner, cat food, coyote lunch, along with every martin, mink, weasel... Keep them penned.
They are VERY efficient at turning scraps into meat. Short life cycle. You may get tired of eating them.
DON'T LET THE KIDS NAME THEM