WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2018 57 Fillet protein content was similar among diets, around 21 percent. Fat content ranged from 3.1 to 3.6 percent. In histological sections of livers of trout fed each diet, no differences were found in the structure of hepatic parenchyma (Figs. 6-8). Discussion and Conclusions Herbivorous, omnivorous and carnivorous fish require more or less the same amount of dietary protein per unit weight, but herbivorous and omnivorous fish use protein and vegetable oils more efficiently than carnivorous fish and require minimal amounts of fishmeal to provide essential amino acids (Naylor et al. 2000). Thus, substitution of protein sources in diets for carnivorous fish such as trout is more complicated. A wide range of feedstuffs have been evaluated as partial fishmeal replacements for rainbow trout diets. These include sunflower meal and soybean meal (Scott et al. (1982), cottonseed flour, soybean meal, and various animal by-products (Lee et al. 2002), chicken poultry concentrate byproduct blend and chicken and egg concentrates (Sealey et al. 2011), and various plant protein sources and synthetic amino acids (Figueiredo-Silva and Lemme (2014). A blend of ingredients of different plant and animal origins and high protein quality is appropriate for this stage of rainbow trout farming. Complete replacement of fishmeal should be tested, as well as continuing the experiments until the full culture cycle is completed. Notes Gustavo Wicki, Oscar Galli Merino, Facundo Sal, Pablo Candarle, Luis Romano and Rolando Hernandez, CENADAC, Subsecretaria de Pesca y Acuicultura, Paseo Colon 982, Buenos Aires, Argentina. Corresponding author: guswicki@gmail.com References Figueiredo-Silva, C. and A. Lemme. 2014. Current challenges and opportunities in amino acid nutrition of salmonids. International Aquafeed 17:16-19. Gomes, E., P. Rema and S. Kaushik. 1995. Replacement of fishmeal by plant proteins in the diet of rainbow trout (Oncorhynchus mykiss): digestibility and growth performance. Aquaculture 130(2-3):177-186. Hintze, J.L. 1998. Number cruncher statistical system (NCSS 2000). Version 6.0. Graphics, Dr Jerry Hintze. Kaysville, Utah, USA. Lee, K.J., K. Dabrowski, J. Blom, S. Bai and P. Stromberg. 2002. A mixture of cottonseed meal, soybean meal and animal byproduct mixture as a fish meal substitute: growth and tissue gossypol isomere in juvenile rainbow trout (Oncorhynchus mykiss) Journal of Animal Physiology, a. Animal Nutrition 86:1-13. Moyano, F., G. Cardenete and M. de la Higuera. 1992. Nutritive value of diets containing a high percentage of vegetables proteins for trout, Oncorhynchus mykiss. Aquatic Living Resources 5:21-39. Naylor, R., R. Goldburg, J. Primavera, N. Kautsky, M. Beveridge, J. Clay, C. Folks, J. Lubchenko, H. Mooney and M. Troell. 2000. Effect of aquaculture on world fish supplies. Nature 405:1017-1024. Robinson, E. and M. Li. 1998. Comparison of practical diets with and without animal protein at various concentrations of dietary protein on performance of channel catfish Ictalurus punctatus raised in earthen ponds. Journal of the World Aquaculture Society 29:273-280. Scott, J., S. Newton and R. Katayama. 1982. Evaluation of sunflower meal as a soybean meal replacement in rainbow trout diets. Proceedings of the 36th Annual Conference of the SE Association of Game and Fish Commissioners. Sealey, W., R. Hardy, F. Barrows, Q. Pan and D. Stone. 2011. Evaluation of 100 percent fish meal substitution with chicken concentrate protein poultry by product blend, and chicken and egg concentrate on growth and disease resistance of juvenile rainbow trout, Oncorhynchus mikyss. Journal of the World Aquaculture Society 42:46-55. Wicki, G. and L. Luchini. 2004. Development of practical diets for pacu a South American freshwater fish species. International Aquafeed 7(3):23- 29 Wicki, G., F. Rossi, S. Panné and L. Luchini. 2008. Cultivo intensivo del “randiá” (Rhamdia quelen) en jaulas suspendidas en estanques, con empleo de diferentes raciones balanceadas y distinta elaboración. In Desarrollo de tecnologías para producción de randiá (Rhamdia quelen). SAGPyA 2008(2):47-67. FIGURE 7. Normal hepatic parenchyma, with a porta space with a bile duct and a branch of the hepatic artery (EP) (H-E, 40x). FIGURE 8. Normal hepatic parenchyma with two bile ducts (CB) (H-E, 40x).
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