Geese just love to nibble on things it doesn't matter if it's alive, try giving them other things to nibble on a head of cabbage hanging inside the pen or brooder. or a head of lettuce . something to occupy their time and make sure what ever your keeping them in is large enough so they aren't cramped. and lots of outside time on nice sunny warm days, with supervision of course. Be sure to offer grit when feeding anything other than their starter feed.
Canada goslings are also attracted to red and we gave them watermelon to help stop that. They love it!