Dietary effects of Clostridium autoethanogenum protein substituting fish meal on growth, intestinal histology and immunity of Pacific white shrimp (Litopenaeus vannamei) based on transcriptome analysis

The study investigated the dietary effects of Clostridium autoethanogenum protein (CAP) substituting fish meal on the growth, intestinal histology, serum immune indexes and transcriptome of Pacific white shrimp, Litopenaeus vannamei. Four isonitrogenous and isolipidic diets were designed as the control diet (CON) containing 560 g/kg fish meal, and three fish meal-substituted diets in which 30% (CAP-30), 45% (CAP-45) and 70% (CAP-70) fish meal were replaced with CAP, respectively. The four diets were fed to shrimp with initial body weight of 2.78 ± 0.13 g for 8 weeks. The results showed that the weight gain, feed intake, survival and intestinal villus height in CAP-45 and CAP-70 groups were lower than those of the control and CAP-30 groups (P < 0.05). In addition, the serum aspartate aminotransferase and phenol oxidase activities in all fish meal-substituted groups, and the lysozyme activity in CAP-45 and CAP-70 groups were increased, while the total protein content in CAP-45 and CAP-70 groups was decreased when compared with the control (P < 0.05). Transcriptome profiling of hepatopancreas indicated that high inclusion of CAP negatively affected the protein synthesis and the utilization of nutrients by regulating pancreas secretion, protein digestion and absorption, ribosome pathways, and disturbed the immune system and metabolic processes by phagosomes and lysosomes pathways, thereby affecting the growth performance and immune function of shrimp. In conclusion, CAP could substitute 30% fish meal in a diet containing 560 g/kg fish meal without adverse effects on the growth, intestinal histology and immunity of Pacific white shrimp.