Effect of dietary
non-protein energy levels on condition and oxidative status of Senegalese
sole (Solea senegalensis) juveniles
R. Rueda-Jasso, L.E.C. Conceição, J. Dias, W. De
Coen, E. Gomes, J. F. Rees, F. Soares, M.T. Dinis, P. Sorgeloos-2004
Aquaculture, 231(1-4): 417-433
Abstract:
The effects of dietary non-protein energy levels on
growth, oxidative status and condition were studied in juveniles of
Senegalese sole (Solea senegalensis). Four isonitrogenous diets with
four energy levels were used: A––low (11% lipid, raw carbohydrate);
B––intermediate (11% lipid, digestible carbohydrate);
C––intermediate (21% lipid, raw carbohydrate); and D––high (21%
lipid, digestible carbohydrate). Survival, relative growth rate (RGR) and
feed conversion rate were not significantly affected by the dietary
treatments. The fatty acid composition of the fish muscle varied little
among the treatments, but trans 18:2n-6, total n-6 and EPA/DHA
ratio, tended to be higher in fish fed diets with low lipid level. Cellular
energy allocation (CEA) results (indicative of metabolic status and net
energy budgets) showed significant differences in liver, but not in muscle
samples. Livers of fish fed diet C contained the lowest carbohydrate,
protein and CEA values, but the highest cellular energy consumption. Fish
fed diet A had the highest CEA for growth, followed by fish fed diets B and
D and then diet C. The liver and muscle peroxidation and antioxidant
activity were measured by thiobarbituric acid reactive substances (TBARS)
test and the enzymatic activities levels of catalase (CAT) and superoxide
dismutase (SOD). TBARS values were higher for fish fed diets with high lipid
content. However, no clear relation was found between HUFA level and TBARS
value. The activity levels of the antioxidant enzymes CAT and SOD were
higher in livers of fish fed diets with a high lipid level. Furthermore, CAT
and SOD activity and TBARS values were influenced by the type of dietary
starch in the diet. Higher oxidation rates were observed in fish fed diets
containing raw carbohydrate. These data suggest that lipid and carbohydrate
energy sources affect the oxidative status of Senegalese sole. Diets
containing low levels of lipid and digestible starch reduce the
susceptibility of the fish to oxidation and may enhance growth rate.
(Laboratory of Aquaculture and Artemia Reference
Center, Ghent University, Rozier 44, B 9000, Ghent, Belgium, e-mail: rebeca_aneli@yahoo.com)