Phase feeding using phosphorus-deficient and phosphorus-replete diets to reduce total P output
The main source of phosphorus discharges to the environment is farmed fish feed. Feeding strategies to reduce phosphorus discharges at source are among the most effective methods of reducing phosphorus discharges from aquaculture production. To this end, the development of high-nutrient feeds and low-phosphorus feeds was examined as an option for reducing phosphorus discharges. Another alternative, which has been less studied, consists of alternating phosphorus-replete feeds with phosphorus-deficient feeds. Depending on the accumulated phosphorus reserves in the biomass, the fish may tolerate relatively long feeding periods during which they receive phosphorus-deficient feed before the first symptoms of phosphorus deficiency appear. These reserves may be replenished following refeeding with phosphorus-replete feed. By alternating phosphorus-replete feeds with phosphorus-deficient feeds, it is possible to reduce phosphorus discharges in fish farm effluent. However, before this objective can be achieved, additional research is needed to understand the dynamics of phosphorus deposition resulting from the use of phosphorus-deficient and phosphorus-replete feeds. Trials conducted with rainbow trout should make it possible to establish the phosphorus balance for cycles of different durations in which feeds (replete and deficient) are delivered on an alternating basis. The ultimate objective of this project is to develop more environmentally-friendly feeding strategies by developing feed formulations that are capable of providing a large variety of phosphorus that is available to fish.
2001 - 2005
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