Influence of dietary composition on growth and energy reserves in tench (Tinca tinca)

The effects of different protein, lipid and carbohydrate diets on growth an d energy storage in tench, Tinca tinca L., were studied. Over a 2-month per iod fish were fed four different diets: control, protein-enriched, carbohyd rate-enriched and lipid-enriched. The best growth rates were obtained with the control and protein-enriched diets; the carbohydrate diet produced the worst results (lowest specific growth rate, weight gain, nutritional index and hepatosomatic index). These results suggest that it is not advisable to reduce dietary fish protein below 35%, and that it is not possible to obta in a protein-sparing effect of either lipids or carbohydrates, at least in our experimental conditions. The high-protein diet resulted in the storage of energy excess as muscle proteins and hepatic glycogen. Tench fed the hig h-carbohydrate diet stored carbohydrates as muscle glycogen and reduced pla sma triglycerides. Finally, both liver and muscle lipid content were in pos itive correlation to dietary lipid.