I heard the Assistant Curator say that they are cutting down on the carrots, parsnips etc as they think the gorillas are getting rather too fat - particularly Salome who has always been the tubbiest.
I don't know why Salome is tubby, but she always has been, even as a young animal at London. At Chessington she became grossly obese- Bristol had their work cut out to get her down to where she is now- even rearing babies doesn't seem to reduce her weight very much.
Isn't Bristol the zoo that started the trend for no-fruit diets for primates? Paignton has followed suit, citing the unhealthy qualities of cultivated fruit (more sugar, less protein and fibre) compared to the fruit they would eat in the wild. The financial savings from cutting out fruit and also root vegetables must be beneficial too.