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

Abstract

It is generally believed that increasing feeding frequency has immediate benefits, 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 Litopenaeus vannamei and accumulation of inorganic nitrogen and phosphorus in the culture water. Shrimp were fed a semi-purified diet containing 19.5% crude protein. Experiment 1 tested five feeding frequencies (3, 5, 8, 11 and 15 feedings day −1) evenly spaced in time during 24 h. Daily ration was divided in similar amounts for each feeding frequency. Mean shrimp survival was 98.6% for all treatments. No significant differences were found either on shrimp growth or accumulation of total inorganic nitrogen (TIN) or total reactive phosphorus (TRP) regardless of feeding frequency. In experiment 2 daily rations were offered manually 1 (100% at 0800 h), 2 (50% each at 0800 and 2000 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) and 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 survival was 100% for all treatments. Although mean shrimp growth was highest at 2 feedings day −1 no significant differences were found among feeding treatments. 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. Levels of TIN were not significantly different among the other feeding treatments. Accumulation of TRP was not significantly different regardless of feeding treatment. These data indicated that under these culture conditions increasing feeding frequency or manipulating ration size did not significantly improve shrimp survival or growth. The only significant environmental effect detected in the culture water was a reduction of TIN at a feeding frequency of 2 compared to 1 and 3 times day −1 in experiment 2. The authors suggest that multiple feedings may not be advantageous for some static culture systems, and that the cost-effectiveness of multiple feedings be evaluated for different feeds and culture systems.