The aim of this project was to analyse critically the potential use of prebiotics in
aquaculture. Initially, the intestinal microflora of rainbow trout, raised in the aquarium
facilities at CEFAS, Weymouth, was investigated using both conventional bacteriological
(culture, BiOLOG) and molecular (Restriction Fragment Length Polymorphism (RFLP),
16S rRNA gene sequencing) techniques. Dominant colony types were identified as
Aeromonas sobria, Carnobacterium piscicola and Clostridium gasigenes.
A series of in vitro growth curve studies was carried out using a selection of
intestinal bacteria and known fish pathogens, to determine the ability of intestinal bacteria
to utilise the potential prebiotic candidates inulin, lactulose and lactitol. Both inhibition
and stimulation of the growth of certain bacteria was noted. Inulin and lactulose were top-dressed
onto commercial trout pellets at levels of 1000mg/Kg and 100mg/Kg and fed to
healthy rainbow trout to determine the effect in vivo. Using Terminal Restriction Fragment
Length Polymorphism (tRFLP) analysis and RFLP analysis, inulin was shown to increase
the growth of Aeromonas sobria and decrease the growth of Clostridium gasigenes in
comparison to samples obtained from fish fed a control diet. Prebiotic supplemented feeds
were both palatable and safe.
To investigate the effect of feeding an inulin-supplemented diet on the
susceptibility of Rainbow trout to Yersinia ruckeri a cohabitation challenge was performed.
Relative percent survival at 55% positive control mortality (RPS55) was 47%. Chi²analysis
showed that differences between the controls and fish fed a diet supplemented with both
100 and 10mg inulin /Kg pellet feed were significant suggesting that inulin can improve
the survival of fish coming into contact with the pathogen Yersinia ruckeri.
Date of Award | 2005 |
---|
Original language | English |
---|
Awarding Institution | |
---|
THE USE OF PREBIOTICS TO IMPROVE FISH HEALTH
STONE, M. (Author). 2005
Student thesis: PhD