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Metabolic effects of changes in the dietary protein: carbohydrate ratio in eel (Anguilla anguilla) and trout (Oncorhynchus mykiss)
Suárez, M.D.; Sanz, A.; Bazoco, J.; García-Gallego, M. (2002). Metabolic effects of changes in the dietary protein: carbohydrate ratio in eel (Anguilla anguilla) and trout (Oncorhynchus mykiss). Aquacult. Int. 10(2): 143-156
In: Aquaculture International. Springer: London. ISSN 0967-6120, more
Peer reviewed article  

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    Carbohydrates; Diet; Diets; Eels; Eels; Fish; Metabolism; Proteins; Trout; Trout; Anguilla anguilla (Linnaeus, 1758) [WoRMS]; Oncorhynchus mykiss (Walbaum, 1792) [WoRMS]; Europe [Marine Regions]; Marine

Authors  Top 
  • Suárez, M.D., correspondent
  • Sanz, A.
  • Bazoco, J.
  • García-Gallego, M.

    The metabolic consequences of the isoenergetic replacement of dietary protein by carbohydrates (CHO) were compared in studies of European eel and rainbow trout. Diets with 45/20, 37/30, 29/40 and 21/50 percent protein/carbohydrate were assessed during a 12-week experiment. The CHO source was pre-gelatinized corn starch. Fish of initial average weight 45 g were fed to satiation twice daily. Weight-gain and feed-efficiency data were generally better in trout than in eel, presumably because trout digestibility coefficients for protein and energy were higher than in eel. In both species, regardless of physiological differences in digestion and absorption, feed intake and nutrient digestibility were lower when dietary CHO was higher, but the inter-species differences decreased with increasing dietary CHO. Pyruvate kinase activity (PK) in trout was not affected by dietary CHO content, while blood-glucose and liver-glycogen levels significantly rose with increasing dietary CHO. In contrast, blood-glucose levels appeared to be regulated in eels, perhaps by an accelerated glycolysis rate, revealed by changes in PK. Gluconeogenic activity was inhibited in trout fed a diet containing 20-30% CHO, while in eels this activity was not inhibited by dietary replacement of protein by carbohydrate. Liver glucose 6-phosphate dehydrogenase activity (G6PDH) was inhibited in trout fed increasing dietary CHO, whereas in eels G6PDH operated at a high rate regardless of dietary composition. These results may indicate that eels have a better capacity for metabolising high-CHO/low-protein diets than do trout.

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