Effects of feeding frequency on growth performance, muscle composition and serum biochemical indices of juvenile <italic>Siganus canaliculatus</italic>

The growth of fish is usually affected by the size and type of bait, feeding frequency, feeding rate and the ability of fish to absorb nutrients. Recent studies have found that feeding frequency is one of the key factors affecting the growth performance of fish. In this study, juvenile Siganus canaliculatus was used as the research object. The growth indices, muscle crude nutrients and serum biochemical indices were measured at different feeding frequencies. According to the physiological and biochemical indices of the fish body, the growth benefit under each feeding frequency was evaluated. The purpose is to find out the scientific feeding frequency for juvenile Siganus canaliculatus, and to provide the corresponding theoretical basis and scientific support for the actual production of Siganus canaliculatus and other fishes. To investigate the effects of feeding frequencies on the growth and physiology of juvenile Siganus canaliculatus, four feeding frequencies (1 meal·d-1, 2 meals·d-1, 3 meals·d-1, 4 meals·d-1) were set, marked as F1, F2, F3 and F4. Three parallel groups were set in each group for 16 weeks in a microfluidic breeding tank (effective volume 125 L). Results of the study showed: 1) Growth indicators: Body weight and body length in each group increased linearly with the breeding time, the growth trend was similar between F3 and F4. The feeding rate and feed conversion ratio were the highest in F3, significantly higher than those of F1 (P<0.05). The hepatosomatic index of F4 was significantly higher than that of F1 (P<0.05), and ratio of intestine weight to body weight and ratio of intestine length to body length of F1 were significantly higher than those of F4 (P<0.05), condition factor of F3 and F4 was significantly higher than that of F1 and F2(P<0.05). 2) Muscle crude nutrition: The muscle moisture content of F1 was significantly higher than that of the other three groups (P<0.05), while the muscle crude protein content of F1 was significantly lower than that of the other three groups (P<0.05). The muscle crude ash content of F2 and F3 was significantly higher than that of F1 and F4 (P<0.05). 3) Serum biochemical indicators: The contents of glucose and total cholesterol were not significantly affected by feeding frequencies. The content of total protein (TP) of F2 and F3 was significantly higher than that of F1 and F4(P<0.05), while the content of albumin (ALB) of F1 and F4 was significantly higher than that of F2 and F3 (P<0.05). The content of triglyceride(TG) increased significantly with the breeding time (P<0.05). The content of high-density lipoprotein (HDL) was the highest in F4, significantly higher than that of F1 and F2 (P<0.05), and the content of low-density lipoprotein (LDL) of F4 was significantly lower than that of other three groups(P<0.05). The activity of aspartate transaminase (AST) and alanine aminotransferase (ALT) was significantly lower than that of the other three groups (P<0.05). Results showed that the optimal growth benefit could be gained at the feeding frequency of 3 meals·d-1.