Effects of Haematococcus pluvialis powder in the diet of golden pompano (Trachinotus ovatus) on the growth performance, pigmentation, hepatic and intestinal health, antioxidant capacity and immunity

Haematococcus pluvialis enriched natural astaxanthin is widely used as a functional additive in the farming industry. The objective of this study was to evaluate the effects of dietary supplementation with H. pluvialis powder on growth performance, pigmentation, hepatic and intestinal morphology, antioxidant capacity, and immunity of golden pompano ( Trachinotus ovatus ). Six isonitrogenous and isolipidic experimental diets, which were formulated to contain 0 % (D1), 0.02 % (D2), 0.04 % (D3), 0.08 % (D4), 0.16 % (D5), and 0.32 % (D6) H. pluvialis powder, were used in the 54-day feeding trial. T. ovatus fed with 0.16 % H. pluvialis showed the greatest levels of FBW, WGR, SGR, and FI. Additionally, across all treatments, the anal fin in the fish given 0.16 % and 0.32 % H. pluvialis displayed increased yellowness (b*), while the tail fin's redness (a*) was considerably higher in the 0.08 % and 0.16 % H. pluvialis treatments. The hepatic morphology result showed that H. pluvialis didn’t influence the health status of the liver, and the activity of CAT decreased in all H. pluvialis -supplemented groups. Compared to other concentrations, the 0.16 % and 0.32 % H. pluvialis groups increased intestinal villi height and amylase activity. The hepatic gene expression showed that 0.16 % H. pluvialis upregulated the expression of kelch ECH-associated protein 1 ( keap1 ), glutathione peroxidase ( gsh-px ), proliferator-activated receptor α ( pparα ), interleukin-10 ( il-10 ), and transforming growth factor β ( tgf-β ), meanwhile, the mRNA level of complement component 4 ( c4 ), superoxide dismutase ( sod ), and sterol regulatory element-binding protein 1 ( srebp1 ) increased in the intestine. Overall, dietary supplementation with 0.16 % H. pluvialis could improve growth performance, pigmentation in fins, digestive capacity of the intestine, and gene expression related to antioxidant capacity, immunity, and lipid metabolism in T. ovatus .