Effects of dietary high amylose on intestinal health of Micropterus salmoides

Carnivorous fish have a very limited ability to use carbohydrates, and excessive carbohydrate will lead to the disorder of sugar metabolism and the decline of immune function, thus inhibiting the growth of fish. Starch as a cheap energy and adhesive in feed, appropriate addition can save protein and reduce feed cost. In order to evaluate the effects of starch structure on intestinal health of Micropterus salmoides, two isonitrogenous and lipid experimental diets were fed with 10% common corn starch (CS) and high amylose corn starch (HACS), respectively. M. salmoides with an initial weight of (8.53±0.06) g were fed for 8 weeks in an indoor system. The results showed that specific growth rate (SGR) and protein efficiency rate (PER) of M. salmoides in HACS group were significantly higher than those in CS group. Meanwhile, the intestinal catalase (CAT) and total superoxide dismutase (T-SOD) activities in HACS group were significantly higher than those in CS group, and the expressions of antioxidant related genes nrf2 and cat were significantly up-regulated. Moreover, compared with CS group, the relative expression levels of pro-inflammatory cytokines (TNF-α and IL-8) in HACS group were significantly down-regulated, while the relative expression levels of anti-inflammatory cytokines (TGF-β) were significantly up-regulated. At the same time, it was observed that the abundance of Cyanobacteria and Lactobacillus in HACS group was significantly increased at phylum level and genus level. It reduced the abundance of potentially harmful bacteria (Acinetobacter, Kocuria). Further phenotypic prediction showed that compared with common corn starch, feeding high amylose corn starch could significantly reduce the proportion of Gram-negative bacteria, increase the proportion of gram-positive bacteria, and significantly reduce the abundance of potential pathogenic bacteria. In conclusion, high amylose maize starch can effectively improve intestinal morphology, antioxidant capacity and immune level, and improve intestinal microflora structure and function of largemouth bass. Therefore, high amylose can improve the intestinal health of M. salmoides.