The following is taken from Rabitlopaedia by Meg Brown and Virginia Richardson.
Most common problem is overfeeding. It helps to feed at a regular time of day.
To keep water from freezing add a little salt or glycerine. Don’t change their diet suddenly.
Young rabbits can be fed pellets from 8 weeks. Large breeds require 4 oz a day plus forgaged greens.
Molasses can be given as an occasional tonic.
Hay needs to be cut short to avoid tangling.
Don’t feed them lettuce, cabbage, parsnips or frozen greens.