|dc.description.abstract||Manufactured feed is one of the important components of commercial shrimp aquaculture, providing nutritional balance for farmed shrimp. However, it is also the primary source causing problems related to water quality. Although feed cost represents a large portion of variable costs in shrimp farming, profoundly influencing the profitability of farm operation, feed use is projected to continue to increase due to rapid expansion of farm intensification. Natural food productivity plays a subordinate role in high density ponds. However, it is still important in providing essential nutrients for shrimp in semi-intensive farms, especially at early stages, and potentially helps to reduce the use of commercial feed if exploited effectively. Adoption of good feed management allows cultured animals to attain nutritional needs from both commercial feed and natural productivity efficiently, improving feed efficiency and reducing wastes derived from commercial feed. Different feeding protocols were evaluated to estimate the effects of feeding rates on growth, FCR and economic returns of L.vannamei shrimp raised in ponds and outdoor tanks. In the first experiment, three feeding protocols were evaluated, including standard feeding protocol (SFP), 10% reduction in the SFP (SFP:90), and 10% increase in the SFP (SFP:110). Shrimp were stocked at a density of 10 shrimp/m2 and harvested after 17 weeks. The results showed that increasing feed by 10% from standard feed ration showed insignificant improvement in mean growth and economic performance. On the other hand, no significant reduction in mean production, survival, FCR and partial return were found for shrimp receiving 10% less feed than typical ration.
In the second experiment, 35 shrimp/m2 were stocked into 24 outdoor tanks that were managed to mimic pond conditions. Six feeding protocols providing a range of feed inputs based on the SFP for tanks (T) were evaluated over six weeks. The results revealed that increasing feed input (T100:110 and T110) did not improve mean growth and FCR, but led to an increase in feed cost per unit of shrimp production. Contrarily, an insignificant reduction in mean growth and survival of shrimp fed with phased feeding protocol (T80:90:100) reduced significantly feed cost per kg shrimp produced, indicating the cost efficiency. Standard feeding protocol (T100) appeared to produce bigger shrimp compared to restricted feeding protocols (T80:90:100, T90 and T90:100), although no significant differences were found except for T90.
The third experiment was conducted in twelve ponds with shrimp stocked at a density of 28 shrimp/m2. Three feeding protocols included standard feeding protocol (SFP), 10% reduction in the SFP (SFP:90), and phased feeding protocol (SFP:80:90:100) in which the feed input was changed at 4-wk intervals starting at 80% during weeks 4-8, 90% weeks 9-12, and 100% weeks 13-16. The results indicated no significant effects on mean growth performance of shrimp restricted to 10% feed input (SFP:90 and SFP:80:90:100). Feed cost was greater for SFP but feed cost per production unit was similar in all treatment. Overall, the findings in these studies demonstrated that increasing the feed ration did not improve growth performance nor economic returns of shrimp raised in ponds conditions. Selection of restricted or full feeding ration depends on the financial status and outcome expectancy of each farm. Feed restriction seems to be more favorable for operations preferring lower investment feed; meanwhile, appropriately practicing standard feeding protocol is encouraged in order to produce shrimp cost-effectively.||en_US