The effect of varying dietary energy on growth and feeding behaviour of common carp, Cyprinus carpio, under experimental conditions

In this study, it was aimed to determine the effects of five isonitrogenous (35% CP) diets I, II, III, IV and V, having respective energy contents 10.85, 11.82, 12.73, 13.69 and 15.06 MJ DE kg−1 on feeding behaviour and growth of common carp with relation to each other. These energetic diets were made by additions of different amount of soy-acid oil with equalizing dietary protein content. Experimental fishes were grouped as Group I, II, III, IV and V. Each group of fish was fed on their respective diet (Group I was fed diet I). Diets were offered to fishes twice a day as two meals at 9:00 a.m. and 17:00 p.m. for 60 days. Behavioural observations were recorded twice a week at 10 min intervals for 1 h period. Fish that had the lowest energetic diet showed the best growth and feed conversion ratio compared to those fed with higher energetic diets (P < 0.05). In addition, fishes that had the lowest energetic diet were more active than the others with respect to total (swimming + foraging + grouping + attention to servicer) activity (P < 0.01). The present results suggested that soy-acid oil should not be used in common carp diet to increase its energy content. Experimental fishes were more active in the mornings than evenings (P < 0.01), showing the common carp is a typical diurnal eater. In conclusion, the current results showed that high energetic diets decreased the appetite of fish, as evidenced the reduction in growth, feed intake, foraging activity and attention to the servicer.