Supplementation of prebiotic compounds, including short-chain fructooligosaccharides (scFOS) has been shown to confer benefits on nutrient utilization, growth, and disease resistance of various animal species through improved gastrointestinal (GI) microbiota. However, potential uses of prebiotics for shrimp have not been defined. A 6-wk feeding trial was conducted in a recirculating system to determine the effects of scFOS supplementation on growth performance, immune functions, and GI microbiota composition of Pacific white shrimp (Litopenaeus vannamei). scFOS was supplemented in a nutritionally complete diet (35% crude protein) at 0.025, 0.0500, 0.075, 0.100, 0.200, 0.400, and 0.800% by weight. After 6 wk of feeding, shrimp fed 0, 0.1, and 0.8% scFOS were sampled for assays of immune function and GI microbiota. Dietary supplementation of scFOS did not improve weight gain, feed conversion ratio, or survival of shrimp. Denaturing gradient gel electrophoresis analysis suggested the intestinal tract microbial community from shrimp fed the basal diet was different from that of shrimp fed the scFOS diets [similarity coefficient (SC) = 74.9%)], although the intestinal tract microbial community from shrimp fed the scFOS-supplemented diets was very similar (SC = 92.3%). All the bacterial species contributing to the GI microbial differences were identified, although most of them are uncultured species. Both total hemocyte count and hemocyte respiratory burst increased (P < 0.05) by incremental dietary supplementation of scFOS (0-0.8%). This study is the first to our knowledge to show that dietary scFOS can selectively support growth of certain bacterial species in the GI tract of shrimp and enhance immunity, which may facilitate development of alternative strategies, including novel probiotics and synbiotics, for shrimp growth and health management.

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Abstract. An intensive growth trial conducted In pens in an earthen pond indicated that growth of Penaeus vannamei (Boone) increased with feeding frequency and suggested that day feedings produce greater growth than night feedings. The differences in growth due to feeding frequency were significant, instantaneous growth rates (IGR) increasing from 1·62% to 1·66% to 1·71%/day as the number of feedings increased from one to two to four per 24 h. Comparison of the IGR of shrimp fed at night (1·64%/day) to that of shrimp fed during the day (1·68%/day) suggested (P= 0·0633) that growth was greater for shrimp given day feedings than for shrimp given night feedings. Survival of shrimp was not significantly different due to feeding frequency or due to time of feeding and averaged 74·7 ± 6·1%. Results indicate that P. vannamei cultured under conditions similar to those tested should be fed a minimum of four times daily and suggest that feeding during the day is at least as good as and may be preferable to feeding at night.

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