Protein Sparing Effect of Carbohydrate on Growth Performance, Digestion Ability of Common Carp (Cyprinus carpio) at Different Feeding Frequencies

Abstract

A 8-week 3 × 2 two-factorial experiment was conducted to investigate effects of dietary carbohydrate levels (5%, 10%, and 20%) and feeding frequencies (fourth daily and twice daily) on the growth, digestion and liver function of common carp (Cyprinus carpio) [initial average weight of (55.37 ± 3.55) g] cultured in floating net cages. Three replicates with 180 common carp were randomly allotted to one treatment with combination of dietary carbohydrate level and feeding frequency in a complete randomized design. The results showed that the weight gain ratio (WGR), special growth ratio (SGR), and protein efficient ratio (PER) were significantly affected by feeding frequency (P < 0.05). Significant effect of feeding frequency on hepatosomatic (HSI) and condition factor (CF) was observed (P < 0.05). Fish fed fourth daily at 5 and 10% dietary carbohydrate levels had significantly higher HSI compared with fish fed twice daily at 5 and 10% dietary carbohydrate levels(P < 0.05). CF was significantly affected by dietary carbohydrate levels (P < 0.05). At 10% dietary carbohydrate level, significant effect on CF of fish fed twice daily was found (P < 0.05), comparing with fish fed fourth daily. Feeding frequency had significant effect on amylase activity of foregut and lipase activity of midgut, and dietary carbohydrate levels significantly affected amylase and lipase activity of midgut (P < 0.05). Lipase activity of fish fed fourth daily at 5% dietary carbohydrate level significantly increased compared to fish fed twice daily at the same carbohydrate level. Comprehensively, the common carp should be fed at 4 meal/d, and the dietary carbohydrate level could be appropriately increased to 5–10%.