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

Aquatic Living Resources, Jul 2010

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.

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

Aquat. Living Resour. Effects of alternating feeding regimes with varying dietary phosphorus levels on growth, mineralization, phosphorus retention and loading of large rainbow trout (Oncorhynchus mykiss ) Gabriel K.D. Koko 0 Pallab K. Sarker 0 Émilie Proulx 0 Grant W. Vandenberg 0 0 Département des sciences animales, Université Laval , Québec (QC), G1K 0A6 , Canada - 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. Alternating feeding regime / Trout / Phosphorus / Loading / Growth 1 Introduction In rainbow trout culture, discharge of phosphorus (P) into the environment arise from feed that is not ingested by the fish, non-digestible P or from absorbed P that exceeds physiological requirements. Excessive P levels in feed, results in excretion of excess or unavailable P as inorganic phosphate mainly in the urine or in the feces (Bureau and Cho 1999; Rodehutscord et al. 2000; Sugiura et al. 2000; Hua et al. 2008; Sarker et al. 2009; Bureau and Hua 2010) . Intensive aquaculture can generate environmental P loadings that may contribute to eutrophication of sensitive receiving water bodies. In the province of Quebec (Canada), the limit for P loading from freshwater trout production is now regulated with a maximum permitted of 4.2 kg ton−1 of fish produced (TFAEDQ 2003) . A number of technologies based on bioengineering, biotechnological, biological and chemical cleaning have been reported to reduce effluent P from aquaculture operation (Summerfelt et al. 1995; Dumas et al. 1998; Hussenot et al. 1998) . Many of these technologies are subject to high initial capital investment, difficulty in controlling critical operational parameters and are not particularly applicable for cage culture operations 1 Supplied the following: (to provide mg kg−1 except as noted): retinyl acetate 2500 IU, cholecalciferol 2400 IU, tocopheryl acetate, 50; menadione, 10; thiamin, 1; riboflavin, 4; pyridoxine, 3; Ca-pantothenate, 20; vitamin B-12, 0.01; niacin, 10; biotin, 0.15; folic acid, 1; choline, 1000; inositol, 300; magnesium carbonate, 1.24 g; calcium carbonate, 2.15 g; potassium chloride, 0.90 g; sodium chloride, 0.40 g; potassium iodide, 0.4; copper sulfate, 30; cobalt sulfate, 0.2; ferric sulfate, 0.20 g; manganese sulfate, 30; zinc sulfate, 40; dibasic calcium phosphate, 5 g; sodium fluoride, 10. 2Sipernat 50: source of acid insoluble ash comprised of 98.5% SiO2 with an average particle size of 50 μm. 3Available P = Total P in diet × ADC of P. (Cripps 1994; Chevalier et al. 20 (...truncated)


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Gabriel K.D. Koko, Pallab K. Sarker, Émilie Proulx, Grant W. Vandenberg. Effects of alternating feeding regimes with varying dietary phosphorus levels on growth, mineralization, phosphorus retention and loading of large rainbow trout (Oncorhynchus mykiss), Aquatic Living Resources, 2010, pp. 277-284, Volume 23, Issue 3, DOI: 10.1051/alr/2010032