i have put my guineapigs out on the grass, with a layer of ripped open cereal box

[SlartyBartFast]

so they have a dry bit,
i have been lettingn the rabbits hop about and felt sorry for the poor pigs.

did i do wrong at this time of year?

their tummies were all wet and muddy
i had to fill their cage with hay and dry the pigs on a teatowel

Pigs don't do well if they get wet and cold it can make them ill they are not robust at all.