Fibreplex also contains:

Probiotics
The live yeast Saccharomyces cerevisiae (CNCM I-4407) 4b1702 to help repopulate the intestine with beneficial micro-organisms.
Preplex prebiotics
A prebiotic, consisting of fructo-oligosaccharide (FOS) and acacia (Gum arabic), to feed and stimulate the growth of beneficial bacteria.

Rabbits can also benefit from Fibreplex if they have a severely reduced appetite, are on a course of antibiotics or have recently had a trauma (such as an operation or injury).