Effects of alternating feeding regimes with varying dietary phosphorus levels on growth, mineralization, phosphorus retention and loading of large rainbow trout (Oncorhynchus mykiss)

Abstract

-Excessive phosphorus (P) levels in freshwater aquaculture effluents are a major environmental problem in certain receiving water bodies. This study aimed to test an approach alternating that alternating feeding P deficient and P sufficient diets and measure P loading from rainbow trout (Oncorhynchus mykiss) culture. Three experimental practical diets consisting of P-deficient (0.4% P, P04), optimum level of P (0.6% P, P06) and P-sufficient as control diet (0.8% P, P08) were formulated. Six different feeding regimes of P-sufficient diet continuously (P08), P-deficient diet continuously (P04), optimum dietary level of P (P06) continuously, one week P-deficient/one week optimum level of P diet (P04/P06.1), 2 weeks P-deficient/2 weeks optimum level of P diet (P04/P06.2) and 4 weeks P-deficient/ 4 weeks optimum level of P diet (P04/P06.4) were tested. Fish were fed twice daily to apparent satiation level 16 weeks. Fish fed all alternating regimes showed growth rate (weight and length) comparable to those of continuous feeding with P08 and P06 diet. The feed conversion ratios (FCR) for all alternating regimes were comparable to that of the P08 and P06 continuous feeding regime. Neither the thermal unit growth coefficient (TGC) nor condition factor (K) significantly influenced by feeding regimes. Vertebrae P, ash and whole body ash content did not differ among regimes. Except fish fed continuous P04 diet, the ash and P content in opercula and whole body total P content were not significantly different among each other in a continuous feeding and alternating feeding schedule. Fish fed all alternating regimes showed significantly lower P consumption than those fed continuously fed with P08 and P06. Different feeding regimes had no effect P retention. Significantly higher P loading (solid and dissolved) was noted in fish fed continuously with P08 diet, in contrast P loading values were lower for all alternating feeding regimes. The study demonstrated that growth and tissue mineralization of fish maintained on alternating feeding regimes with P04 and P06 diet were comparable to those continuously fed with diet of P08. These results demonstrate that it is possible to reduce P intake by 34% and reduce P loading 52% by adopting alternating feeding regimes compared to P08 diet. This study provides evidence that alternating feeding of P deficient and optimum dietary levels using practical ingredients can be adopted as a means of reducing P loading from rainbow trout culture without compromising growth.

Reducing geosmin off-flavor compounds and waste outputs through dietary phosphorus management in rainbow trout aquaculture

“…This phenomenon has also been observed in large fish. For instance, Koko et al (2010) found that changes in weight of 164 g trout fed deficient P (4.0 g kg −1 diet) and sufficient P (8.0 g kg −1 diet) over time remained similar during the initial 56 d. After this period, poor growth performance and a number of visual deficiency signs were observed, such as bone deformities in the tail regions of trout fed the P-deficient diet. However, there were no visual signs of P deficiency in the current study.…”

“…The growth performance of fish in the current study confirmed that the LP (5.4 g kg −1 diet) diet had sufficient total P to satisfy the minimum requirement for large rainbow trout. In large fish, the focus of the present study, the requirement for P is known to de crease with age because the growth rate decreases and dietary P is used mainly for maintaining meta bolic functions (Lellis et al 2004, Koko et al 2010). The P content of the LP diet was in the range of the dietary P requirement that has been reported for normal growth of rainbow trout, 4.0−6.0 g kg −1 (Ketola & Richmond 1994, Rodehutscord 1996.…”

Preliminary study for phenotypic description of vertebral abnormalities in triploid trout subjected to prolonged deficiency in phosphorus

“… 2 Estimations based on open formulation developed by University of Guelph (Canada) and previous experiments (Koko et al., ). Plant origin phytate‐P (%) was calculated from measures on each ingredient = 0.3 for corn gluten, 0.4 for soybean, 0.4 for wheat flour and 0.09 for wheat gluten.…”

Taxonomy of Means and Ends in Aquaculture Production—Part 2: The Technical Solutions of Controlling Solids, Dissolved Gasses and pH

“…It is important to remember that feeding frequency and regime could greatly influence the production of waste (e.g., solids and P and N compounds), causing peaks in its concentration [12][13][14][15] which requires increased capacity in certain treatment functions. Practicing continuous or high feeding rates, however, would result in more stable production of waste, lowering the treatment capacity requirements.…”