Physiological and transcriptomic effects of formulated diets including the prebiotics inulin, -glucan, and chitosan on juveniles of Totoaba macdonaldi

In this study, we evaluated the effects of three prebiotics (inulin, beta-glucan, and chitosan) on the physiological performance of Totoaba macdonaldi juveniles under culture conditions. The respiratory burst and the leucocyte content were measured in the blood to assess innate immune responses. The intestinal digestive capacity was evaluated by analyzing trypsin, amylase, and lipase activities, whereas the effects of such prebiotics at the transcriptomic level were assessed by implementing the RNA-Seq of liver tissue. After 60 days, fish fed with 0.5% chitosan diets showed the highest respiratory burst, the lowest lipase activity, and the highest number of differentially expressed genes (DEGs), where biological processes related to proteolysis, digestion, and lipid hydroxylation were the most affected. In addition, fish from the chitosan diet showed the highest expression of immunoglobulin genes. In contrast, fish fed with the 1% inulin diet presented the highest diet digestibility and trypsin and lipase activities. These physiological effects align with the highest expression of trypsin-like and chymotrypsin-like genes in the liver of fish from this diet. On the other hand, fish fed the 0.1% beta-glucan diets showed the lowest amount of DEGs compared to the control group, most of which were associated with immune response, with an up-regulation of genes related to the complement system and a downregulation of immunoglobulin genes. Based on our results, we propose the inclusion of 1% dietary inulin to improve the digestibility of experimental diets and the addition of 0.5% chitosan to stimulate the immune system of T. macdonaldi juveniles.