Oil source regulates intestinal health of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu): Structure, inflammation and microorganisms homeostasis

The price and yield of fish oil limits the development of aquaculture, plant oils as an alternative to fish oil can ensure the sustainable development of the aquaculture industry, but a series of negative effects caused by plant oils limit its application. To overcome these negative factors, it is important to further explore the regulatory sites and mechanisms of plant oils, particularly the intestinal tract as the digestive and absorptive site and one of the immune organs, and therefore the aim of the present study is to investigate the regulation of grouper intestinal structure, immune status and bacteriological homeostasis by different oil sources. Supplying 7 diets with fish oil, corn oil, sunflower oil, tea oil, olive oil, rice oil and mixed oil (above six equivalents were mixed) as lipid sources to juvenile hybrid grouper for 8 weeks, the intestinal morphological structure, intestinal inflammation and antioxidant-related factors and microbial composition and functional predictions were analyzed. The results showed that plant oils caused impaired intestinal structural integrity and inflammatory responses in grouper, as well as imbalance in intestinal microbial homeostasis, especially in the sunflower oil group, followed by corn oil. On the contrary, olive oil protected the intestinal structural integrity from damage, upregulated the expression of anti-inflammatory factors and antioxidant genes, and enhanced the relative abundance of intestinal probiotic bacteria, which had a protective effect on intestinal health. Above results implied that the structural damage and inflammatory response of intestine caused by most plant oils during fish oil replacement may be related to bacterial imbalance, while olive oil may have a protective effect on intestinal health and structure by increasing the relative abundance of intestinal probiotics, with potential for further in-depth exploration.