Abstract
The present research examined the impact of sodium humate (SH) in feed on the intestinal health of genetically improved farmed tilapia (GIFT, Oreochromis niloticus). GIFT with average weight of 3.9 g were provided with diets incorporated diverse content of SH from low to high (0%, 0.1%, 0.2%, 0.4%, and 0.6%, denoted as SH0, SH1, SH2, SH4, and SH6) for 63 days. Results indicated that incorporating 0.4%-0.6% SH into the diet significantly reduced the plasma lactulose/rhamnose ratio, while plasma diamine oxidase (DAO) activity was depressed by supplementation with 0.1%-0.4% SH (p < 0.05). Dietary SH level increased the length and width of villu, as well as the levels of polymeric immunoglobulin receptor in the distal intestine (DI). The SH2 group exhibited elevated levels of interleukin (IL)-10 in the DI and transforming growth factor β1 (TGF-β1) and IL-1β in the proximal intestine (PI). On the other hand, the contents of tumor necrosis factor-α (TNF-α) in the middle intestine (MI), IL-1β, and IL-6 in the MI and the PI were generally lower in the SH groups contrast to the SH0 group, while interferon-gamma (IFN-γ) and IL-8 levels in the DI showed the opposite trend. Additionally, dietary inclusion of 0.2% SH promoted the intestinal microbiota species diversity and relative abundance of Cetobacterium, with SH6 group displaying the highest complexity. Overall, dietary SH supplementation improved intestinal health of GIFT by decreasing mucosal permeability, improving intestinal absorption surface area, enhancing intestinal immune barrier, and reduce inflammation. The recommended level of SH was 0.2%-0.4% of diet for GIFT.