ours dont mind a change to much... with all the ups and down with my (now late) father in law, we deliberately dont have strict timed routines so all the animals accept variety.
its the spice of life after all !
Once its dark, the pigs go off inside and get up to the sound of a feed bin being opened, if we havent managed to feed them before then. Mind you, any time of day you go near the feed bin, they call out to be fed!