Sparing effect of pond water on vitamins in shrimp diets

Abstract

A 10-wk experiment was conducted to determine whether shrimp pond water has a sparing effect on vitamins, trace minerals, and protein levels in diets fed to juvenile Pacific white shrimp, Litopenaeus vannamei. Twenty-four 52-L aquaria were stocked with 0.7-g shrimp at a density of 24 shrimp/aquaria (100 shrimp/m 2 equivalent). Shrimp were exposed to flow-through seawater from one of two sources: clear well water from a seawater aquifer or organically rich water from a pond used for intensive shrimp culture. In addition, four diets were evaluated in each of the two water sources (three replicates/treatment), including: 1) a 35%-protein diet with vitamin and trace mineral premixes, 2) the same 35%-protein diet minus the vitamin premix, 3) the 35%-protein diet minus the trace mineral premix, and 4) a 25%-protein diet with vitamin and trace mineral premixes. Shrimp grown in well water without vitamins in their diet had a significantly lower ( P < 0.05) final weight, growth rate, and survival, and a significantly higher FCR, than shrimp grown in well water with vitamins. However, there was no significant difference in final weight, growth rate, survival, or FCR between pond-water reared shrimp with and without vitamins, indicating that removal of vitamins from the diet of pond water-reared shrimp had no effect on shrimp performance. In contrast to vitamins, there was no sparing effect of pond water on trace minerals or protein levels. As expected, growth rates of shrimp reared in pond water were greater than those in well water for each of the four diets. The largest difference in growth rate was seen with the 35%-protein diet minus vitamins. Shrimp fed this diet grew 306% faster in pond water than in well water. It appears that the growth enhancing effect of pond water is more pronounced when shrimp are fed diets of inferior quality. Results from this study indicate that pond water has a sparing effect on vitamins in shrimp diets, and microbes likely contributed significantly to this effect. By exploiting endogenously produced microbes and associated detritus, shrimp farmers and feed manufacturers can reduce substantially vitamin levels in shrimp feeds, resulting in reduced feed costs without compromising shrimp growth, survival, or FCR.