Diet manipulation to control water quality in an intensive system

Objective: Limitation of natural resources such as water and land has been resulted in intensification of production systems. However, intensification has its drawbacks, lead to an increased waste accumulation within production system. High levels of pollutants can reduce growth and increase the incidence of disease. The accumulation of solids in intensive system increase stress in fish. Management of water quality may be achieved through controlling the amount and removal efficiency of produced waste. The main goal of this study was to investigate weather diet composition have a significant impact on the water quality in the intensive system. Method & Materials: Aquaculture waste can be divided into solid waste and dissolved waste. Manipulation of diet composition alter total amount of produced waste and also faecal physical properties. Different diets were used to test the hypothesis: highly digestible diet versus low digestible diet; high protein diet versus low protein diets and diet which leads to higher faecal removal efficiency versus diet which lead to lower faecal removal efficiency. The experiment was conducted in the recirculation system with high fish density. Water quality parameters were measured regularly. Results & Conclusion: Reduction of faeces removal efficiency by addition of guar gum to the diet increased suspended solid production leading to an increased ammonium and nitrite concentration and decreased dissolved oxygen in the system water. This condition increased the amount of solid undergoing bacterial decomposition, lead to a reduced nitrification rate. Water quality parameters, such as suspended solid and COD significantly reduced by the use of highly digestible diet. The reduction of nitrogen waste is achieved by decreasing diet dietary protein in comparison to diet containing larger nitrogen content. Lower nitrogen loading of the culture water induced by dietary composition can increase carrying capacity of an intensive system without adverse effect on growth and/or health. Lowprotein- diet also reduces the make-up water consumption by 60% via a positive influence on water quality. In conclusion water quality in an intensive system can be managed through reduction in dissolved waste excretion and increase in faeces removal efficiency caused by feed composition.

کلیدواژه ها:

Water quality ، Waste ، Intensive system ، dietary composition