February 15-18, 2009 Washington State Convention Center Seattle ...

EFFECTS OF DIETARY PREBIOTICS ON MICROBIAL COMPOSITION AND INTESTINAL
STRUCTURE OF JUVENILE RED DRUM Sciaenops ocellatus FED SOYBEAN-BASED DIETS
J. Alejandro Buentello*, Camilo Pohlenz, Gary Burr and Delbert Gatlin, III
Department of Wildlife and Fisheries Sciences
Texas A&M University System
College Station, Texas 77843-2258 USA
abuentello@tamu.edu
Prebiotics are non-digestible functional ingredients that beneficially affect the host by stimulating the growth and/or activity
of one or a limited number of bacteria in the gastrointestinal (GI) tract, thus improving the host’s enteric health. However,
prebiotic use also has proven to benefit the rapidly changing intestinal morphology of juvenile vertebrates by preventing villous
atrophy and eliciting cyto-protective effects on sloughing cells of the GI mucosa. Prior experiments in our laboratory
have demonstrated desirable effects of dietary prebiotic supplementation on red drum including enhanced nutrient availability,
improved growth performance, feed efficiency and disease resistance. Therefore, this experiment was conducted to assess
the effects of fructooligosaccharide (FOS) in the form of inulin, mannanoligosaccharide (MOS), transgalactooligosaccharide
(TOS), and GroBiotic ® -A (GBA) on gut structure and intestinal changes of microbial populations of juvenile red drum fed
soybean-based diets.
Experimental fish (10.9 ± 0.2 g/fish, initial weight) were acclimated for 2 weeks to the trial conditions and fed a basal diet in
which half of the dietary protein (40%) was provided by soybean meal with the other half from menhaden fishmeal. Experimental
diets incorporated FOS, MOS, TOS or GBA at 1% by weight to the basal diet. These diets were formulated to satisfy
all known nutrient requirements of red drum, provided equal digestible energy, and were fed to apparent satiation, twice daily
to triplicate groups of fish. Brackish water (10 ppt) was recirculated through 110-L aquaria at 1 L/min and kept at 26 ± 1 C,
with approximately 100% oxygen saturation and < 0.5 mg/L unionized ammonia. After a 4-week period, proximal and distal
intestine samples from three fish per aquarium were collected for determination of selected histometric indicators. Each sample
was externally and internally washed with NaCl 0.9% to remove the intestinal contents. Samples were individually transferred
to jars containing 10% buffered formalin, for fixation. After a 15-day fixation period, samples were embedded in paraffin,
sectioned to a 2 to 5-μm thickness, mounted on glass slides, and stained with hematoxylin and eosin. Denaturing gradient gel
electrophoresis (DGGE) analysis including DNA sequencing and real-time polymerase chain reaction analyses were also utilized
to characterize changes in GI tract microbiota upon prebiotic treatment. Data on microvilli height, width and density of
proximal and distal intestine are under analytical review. Based on preliminary assessment of these data, it appears that GBA,
MOS and TOS significantly altered the microbial population structure in the GI tract of juvenile red drum. Also, prebiotic
inclusion appeared to increase microvillous height and density.
Taken together, these results suggest that inclusion of these prebiotics at 1% of diet is adequate to elicit structural changes while
stimulating villi growth in the fish intestine. Likewise, prebiotic treatments appear to selectively stimulate the proliferation
of certain bacterial species. This information is likely to facilitate development of alternative strategies, including prebiotics,
probiotics and synbiotics, to improve fish growth and health management.
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