Effects of Dietary Fish Meal Replacement with Composite Mixture of Chicken Meal, Krill Meal, and Plant Proteins on Growth, Physiological Metabolism, and Intestinal Microbiota of Chinese Perch (Siniperca chuatsi)

This trial aimed to investigate the influence of graded replacing fish meal (D1: 0.00%, D2: 27.27%, and D3: 54.55%) with mixed protein ingredients (i.e., chicken meal, krill meal, fermented soybean meal, and soy protein concentrate) on the growth performance, muscle nutritional composition, blood biochemical indices, gut bacterial community, and transcriptome of Chinese perch. Two hundred seventy Chinese perch were divided into three groups (90 per group) and the diet lasted for 56 days. Results showed that the weight gain rate and specific growth rate were significantly lower, and the feed conversion ratio was significantly higher in the D3 group than in fish fed D1 (P<0.05), with no significant differences between the D1 and D2 groups (P>0.05). The muscle crude protein content was highest in the D2 group, and the crude fat content was significantly different in the order: D3 > D1 > D2 (P<0.05). The levels of serum triglycerides (TG) and low-density lipoprotein cholesterol in the D2 group were significantly lower than those in the D1 group (P<0.05), but there was no significant difference compared to the D3 group (P>0.05). The microbial community structure changed significantly. Mycoplasma showed the highest abundance in the D1 and D2 groups (P<0.05), and Cetobacterium peaked in D2 group, and significantly higher than that in D1 group (P<0.05). Network analysis and cohesion index calculation showed that both network complexity and cohesion peaked in D2 group, and Cetobacterium was highly correlated with the cohesion index (P<0.05). Further, muscle transcriptome analysis results showed that compared with the control group, differentially expressed genes were clustered (Q < 0.05) in the arginine and proline metabolism pathways in D2 group. Fish in D3 group significantly (Q < 0.05) affected genes involved in KEGG pathways of ribosome, circadian rhythm, thermogenesis, insulin signaling pathway, fatty acid degradation, oxidative phosphorylation, and apoptosis. In conclusion, under the experimental conditions, the replacement of 27.27% of fish meal by the compound protein did not have a negative impact on the growth performance of Chinese perch and could improve muscle quality, lipid metabolism, and the interaction of intestinal microbiota.