The use of rotifers as live food for larval fish continues to be an important part of larviculture of various fish species including southern flounder. However, the nutritional composition of rotifers is generally considered inferior to other live foods such as copepods. The present study evaluated the application of four different types of nutritional supplements to rotifers (Branchionus plicatilis and ?Brachionus manjavacas) including probiotics, prebiotics, vitamin C, and taurine to determine how they may influence rotifer production and microbial composition, as well as nutrient concentrations. Separate trials were conducted to evaluate changes in the production and microbial composition of rotifers exposed to the probiotics Bactocell® and Aquablend (produced by BIO-CAT) and the prebiotic GroBiotic®-A (International Ingredient Corporation) added to the culture water during 4-day production cycles compared to the control with no supplement. GroBiotic®-A in two separate trials showed increased rotifer production. Denaturing gel gradient electrophoresis (DGGE) analysis demonstrated rotifers cultured with the aforementioned additives had altered microbiota composition compared to the control as noted for the GroBiotic-A treatment in Fig. 1
Vitamin C supplementation was evaluated in two separate trials in which Brachionus manjavacas was enriched with various concentrations of ascorbic acid in the culture media. Results showed that rotifers exposed to 4 g of ascorbic acid/liter contained the highest concentration of ascorbic acid averaging 2,308 μg/mg rotifer compared to the treatment without ascorbic acid exposure averaging 360 μg/mg rotifer. Optimization of rotifer production required adjustment of pH in the culture media. Two separate trials also examined the effects of taurine enrichment of rotifers. Taurine was supplemented at either 0, 1, or 2 g/liter and blended with Amplifeed™ Replete after which samples were collected at 1, 2, 4, 8, and 24 h post feeding. Amino acid analysis indicated that taurine supplementation resulted in a dose-dependent increase in taurine concentrations of rotifers with 2 g/liter yielding the highest concentration of taurine which was maintained at 1.13 g taurine/100 g samples at 4 h after feeding.
Details from these trials will be presented to demonstrate that the nutritional and microbial composition of rotifers can be effectively altered to improve their nutritional value to larval fish.