| dc.description.abstract | Prebiotic compounds comprise a group of dietary supplements defined as nonviable
food ingredients that are selectively metabolized to favor beneficial intestinal
bacteria. Such bacteria may confer various desirable effects including enhanced disease
resistance and nutrient availability to the host.
This study examined the effects of four prebiotics, GroBiotic®-A (a mixture of
partially autolyzed brewers yeast, dairy ingredient components and dried fermentation
products), mannanoligosaccharide (MOS), galactooligosaccharide (GOS), and the
fructooligosaccharide (FOS) inulin on digestibility of soybean-meal-based diets by
goldfish. A basal diet was formulated so that 50% of the protein was provided by
soybean meal and the other 50% was from menhaden fishmeal. Each prebiotic was
supplemented to the basal diet at 1% by weight. A diet containing all of its protein from
menhaden fish meal also was prepared as a control diet. Chromic oxide was added to
the diets at 1% as an inert marker. Each diet was fed to adult goldfish in duplicate 110-L
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aquaria for a total of 8 weeks. The dried fecal material from each aquarium was pooled
over time and analyzed for protein, lipid, organic matter and chromium in order to
compute coefficients of apparent digestibility. Genomic DNA of gut microbiota also was
isolated from the fecal samples of goldfish fed the various diets and subjected to
polymerase chain reaction (PCR) using bacteria-specific PCR primers to conserved
regions flanking the variable V3 region of 16S rDNA. Then, denaturing gradient gel
electrophoresis (DGGE) of the resulting amplicons was conducted as a means of
assessing diversity of microbiota in the gastrointestinal (GI) tract.
Results of the present study revealed that none of the prebiotics affected apparent
digestibility coefficients of the soybean-meal-based diet compared to the basal diet,
although the diet supplemented with MOS consistently yielded the lowest values. In
addition, goldfish digested the soybean-meal-based diets as well as the control diet.
DGGE analysis revealed no differences in microbiota of goldfish fed the various
prebiotics. These results are in contrast to those obtained with carnivorous fish species
such as the red drum (Sciaenops ocellatus) in which the prebiotics increased digestibility
coefficients of soybean-meal-based diets and altered GI tract microbiota. | en |
