Effects of dietary two different microencapsulated Origanum oils on growth performance, nonspecific immunity, gut bacterial communities, and disease resistance in Micropterus salmoides

Abstract

This study was conducted to examine the effects of two types microencapsulated Origanum oils (MOO) (HMOO: hot spray microencapsulated Origanum oils; CMOO: cold spray microencapsulated Origanum oils) supplemented at different levels (0, 100, 200, and 300 mg/kg) on growth performance, antioxidant ability, nonspecific immune responses, gut bacterial communities, gut histology, and disease resistance of juvenile largemouth black bass (mean body weight = 9.72 g). The growth performance were significantly improved in both HMOO and CMOO groups (P < 0.05), but there was no significant interaction between different dietary microencapsulation technologies and supplemented dosages (P > 0.05). A significant interaction between the microencapsulation techniques and dosages was observed in some parameters (e.g., CAT, SOD, GSH-PX, MDA, LYZ, AKP, and ACP) of serum, liver, and intestine, which were influenced by MOO dosage. The α diversity index (observed_species, Chao1, and ACE) of intestinal bacteria and the relative abundance of certain bacterial taxa (Fusobacteriota, Proteobacteria, Cetobacterium, Plesiomonas, and Romboutsia) were significantly affected by different MOO supplemental levels (P < 0.05), where the former was significantly affected by the interaction of microencapsulation technology and dose, while the latter was not affected by the interaction (P > 0.05). Villus height and disease resistance increased in the HMOO groups with different MOO dosages (P < 0.05), but no significant difference was found between the microencapsulation techniques (P > 0.05). HMOO had more positive effects on villus height and disease resistance than CMOO. In conclusion, the effects of MOO on black bass were more dependent on the supplemental dosage than the microencapsulation techniques.