Not exactly sue what it is about citrus , Only thing I can think of would be the high content of citric acid .. I feed mostly a mix of baby food for my fruit , but every couple of weeks I make up a batch of fresh I just cut it up in small chunks and throw it in the blender. I have even taken unsweetened fruit cocktail and blended it before and they seem to like it alot, its mostly peaches and pears when ever I make a batch up I freeze it in ice cube trays and mix the calcium in as im going