My geese have started doing the mating rituals. The males are dancing with eachother with their necks interlaced. I haven't seen too much breeding, although I did find a broken goose egg near the workshop. So I have to keep my eyes open and start collecting eggs for the incubator. God I love...
I make hay here, and the geese do eat it. Some of then go into the goat pen at night and they just merrily chomp away at the round bales. I don't think they could live entirely on hay though, but I don't see it as being adverse as long as they have water available.
Any poultry food will work. I wouldn't over feed them layer feed, though. But, if you want them to put down some eggs this winter, some free choice oyster shell would be a nice idea.
I finish my geese on broiler feed, so I know they enjoy eating that. The ones I keep overwinter usually keep...