Vets often prescribe Royal Canin but there are others on the market as good or better and inexpensive. One of my girls is sensitive to grains. I buy from Zooplus but most outlets carry a wide selection. I usually get Kattovit sensitive, James Wellbeloved or Greenwoods which is a supplementary food but I alternate other brand's complete food (wet and dry) which are grain free. I almost always buy easy to digest chicken or turkey and they both love rabbit. India has been so much happier since I changed them both to completely grain free. I ring the changes regularly and try other grain free brands from time to time and they eat everything I put down. It took me ages to find brands that fulfilled what was required but that weren't too expensive but now I know what suits them and me.