Objective This research aimed to investigate the impacts of diets with different ratios of starch to cellulose on the growth, and physiological and biochemical indices of common carp (Cyprinus carpio). The findings were intended to provide a theoretical foundation for the scientific and rational formulation of the proportion of starch and cellulose in common carp compound diets.
Method In this experiment, the ratios of starch to cellulose in the diets were set as follows: 0.36 (group A), 0.65 (group B), 1.11 (group C), 1.92 (group D), 2.80 (group E), and 11.67 (group F). After 80 days of feeding the common carp, samples were collected for the analysis of physiological and biochemical indices.
Result After 80 d, the weight gain rate of group E was the highest, reaching 1146±349%, and the feed conversion ratio was the highest at 77.30±0.81. Group F exhibited the highest specific growth rate and hepatosomatic index, which were 3.09±0.32% and 1.84±0.03%, respectively. The growth rate of the low-starch content diet groups (groups A-C) was generally lower than that of the high-starch content diet groups (groups D-F). The final condition factor of groups C and D remained between 2.51 and 2.68, within a reasonable range. Among them, group C had the most stable body shape, with a condition factor variation of 11.80±6.61%. Diets from different groups had significant effects on the liver function and metabolism of common carp. The activities of alanine aminotransferase (ALT) (48.88-53.00 U/L)) and aspartate aminotransferase (AST) (453.67-500.33 U/L)) in groups C and D were relatively lower compared to those in other experimental groups. Other liver function-related indicators were maintained at normal levels, indicating minimal liver damage. Conversely, diets with starch/cellulose ratios lower than 1 or higher than 2 (groups A, B, E, and F) led to substantial liver damage in common carp, with significantly abnormal related indicators.When examining the effects of extremely high cellulose (group A) and extremely high starch (group F) diets on the muscle fatty acid composition of common carp, it was found that the essential fatty acid linoleic acid (C18: 2n6c) content in group A was significantly higher than that in group F (P < 0.01), indicating that the diet in group F significantly influenced the lipid metabolism of common carp.
Conclusion The use of diets with excessive starch and cellulose content affects the growth and development of common carp. For common carp diets, the optimal ratio of starch to cellulose should be controlled within the range of 1 ∶ 1 to 2 ∶ 1. The most suitable starch content is 20%-25%, and the cellulose content is 10%-13%.
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