Coenzyme Q10 (CoQ10) is a powerful antioxidant that is gradually being used in aquafeeds. Here, we examined the influence of oxidized fish oil and CoQ10 supplementation on intestinal microbiota of Micropterus salmoides at different growth stages. Three isonitrogenous and isoenergetic diets were formulated to contain 100% fresh fish oil (FFO), 100% oxidized fish oil (OFO) and OFO + 0.1% CoQ10 (QFO) and were fed to Micropterus salmoides (95 ± 0.60 g) for 70 days. Furthermore, three different growth stages (28-day, 49-day, 70-day) were selected to observe the dynamic changes of intestinal microbiota. The growth performance of fish fed QFO were significantly higher than that of fish fed OFO after a 70-day’s feeding. Intestinal microbial community of Micropterus salmoides was significantly affected by different growth stages more than diets. The abundance of phylum Proteobacteria showed an increasing trend, while the abundance of Firmicutes decreased with increased feeding time. Compared with OFO, diet supplemented with CoQ10 significantly increased the abundance of Firmicutes, and decreased Proteobacteria on the 28- and 70-day of feeding. When fish fed OFO and QFO, Simpson and Shannon indices significantly increased with increased feeding time from 28 to 70 days. Fish fed QFO significantly decreased the value of Bray-Curtis distance than those fed FFO on the 70-day of feeding. Moreover, Bray-Curtis distance showed an increased trend with increased feeding time. Notably, intestinal microbial functional prediction indicated that OFO suppressed amino acid metabolism, while long-term oral administration of CoQ10 could improve amino acid metabolism and detoxification of Micropterus salmoides. This study demonstrated that prolonged application of CoQ10 is needed to produce some beneficial effects to Micropterus salmoides.

The aim of this experiment was to investigate whether dietary coenzyme Q10 could alleviate stress response of Micropterus salmoides caused by oxidized fish oil. Four isonitrogenous and isoenergetic diets were formulated to contain 100% fresh fish oil (FFO), 50% fresh fish oil + 50% oxidized fish oil (BFO), 100% oxidized fish oil (OFO) and 100% oxidized fish oil + 0.1% coenzyme Q10 (QFO) and were fed to Micropterus salmoides (95 ± 0.60 g) for 70 days. Higher weight gain rate was recorded in fish fed diet supplemented with coenzyme Q10 (CoQ10). FFO and BFO significantly increased contents of fat and energy in whole-body, while protein and energy retention significantly decreased in fish fed OFO. Apparent digestibility of energy and fat showed a significant decrease trend with increased the proportion of dietary oxidized fish oil. Fish fed OFO significantly increased activities of superoxide dismutase and catalase, while CoQ10 supplementation significantly reduced activities of alanine aminotransferase and aspartate aminotransferase in plasma. Contents of n-3 polyunsaturated fatty acids and highly unsaturated fatty acids, especially EPA and DHA in liver and muscle significantly decreased in fish fed OFO. Transcriptome analysis indicated that a total of 1238, 1189 and 1773 differentially expressed genes (DEGs, |log2(fold change) | >= 1 and q-value<=0.001) were found in the three comparison groups (FFO vs. OFO, FFO vs. QFO, OFO vs. QFO), respectively. After KEGG enrichment, the main changed pathways in the two comparison groups (FFO vs. OFO, OFO vs. QFO) related to the immune system. Dietary OFO up-regulated the expression of immune-related genes and inflammatory factors, while dietary CoQ10 supplementation reduced these effects.