Effect of variations in daily feeding frequency and ration size on growth of shrimp, Litopenaeus vannamei (Boone), in zero-water exchange culture tanks

It is generally believed that increasing feeding frequency has immediate be nefits, including reduced nutrient leaching and increased shrimp growth. In this study, static-water ecoassays were conducted to determine the effect of feeding frequency and percentage of daily ration on growth of Litopenaeu s vannamei and accumulation of inorganic nitrogen and phosphorus in the cul ture water. Shrimp were fed a semi-purified diet containing 19.5% crude pro tein. Experiment 1 tested five feeding frequencies (3, 5, 8, 11 and 15 feed ings day(-1)) evenly spaced in time during 24 h. Daily ration was divided i n similar amounts for each feeding frequency. Mean shrimp survival was 98.6 % for all treatments. No significant differences were found either on shrim p growth or accumulation of total inorganic nitrogen (TIN) or total reactiv e phosphorus (TRP) regardless of feeding frequency. In experiment 2 daily r ations were offered manually 1 (100% at 0800 h), 2 (50% each at 0800 and 20 00 h), 3 (33% each at 0800, 1400 and 2000 h), 3(+) (45, 20 and 35% at 0800, 1400 and 2000 h, respectively), 4 (25% each at 0800, 1200, 1600 and 2000 h ), 4(+) (40, 15, 15 and 30% at 0800, 1200, 1600 and 2000 h, respectively) a nd 6 (16.6% each at 0800, 1030, 1300, 1600, 1800 and 2000 h) times day(-1); and with automatic feeders 15 times day(-1) (every 96 min). Shrimp surviva l was 100% for all treatments. Although mean shrimp growth was highest at 2 feedings day(-1) no significant differences were found among feeding treat ments. Accumulation of TIN in the culture water was significantly lower for tanks receiving feed 2 times day(-1) compared to 1 and 3 times day(-1). Le vels of TIN were not significantly different among the other feeding treatm ents. Accumulation of TRP was not significantly different regardless of fee ding treatment. These data indicated that under these culture conditions in creasing feeding frequency or manipulating ration size did not significantl y improve shrimp survival or growth. The only significant environmental eff ect detected in the culture water was a reduction of TIN at a feeding frequ ency of 2 compared to 1 and 3 times day(-1) in experiment 2. The authors su ggest that multiple feedings may not be advantageous for some static cultur e systems, and that the cost-effectiveness of multiple feedings be evaluate d for different feeds and culture systems. (C) 1999 Elsevier Science B.V. A ll rights reserved.