Effects of dietary astaxanthin supplementation on growth performance, antioxidant status, immune response, and intestinal health of rainbow trout (Oncorhynchus mykiss)

Abstract

A feeding trial was conducted to assess the impacts of dietary astaxanthin from wall-broken Haematococcus pluvialis (WBHPA) on the growth performance, antioxidant status, immune response, and intestinal health of rainbow trout (Oncorhynchus mykiss). Six experimental diets were formulated with various concentrations of WBHPA, ranging from 0 to 8.4 g/kg (containing 0 to 125 mg/kg astaxanthin). Each diet was fed to triplicate groups of rainbow trout (mean initial weight of 561 g) twice daily for 9 consecutive weeks. The survival rate and feed intake of fish exhibited no significant differences among the dietary groups (P > 0.05). Similarly, dietary inclusion of 25 to 100 mg/kg astaxanthin did not significantly affect the weight gain and daily growth coefficient (P > 0.05), but excessive inclusion of astaxanthin (125 mg/kg) slightly depressed these parameters (P < 0.05). Dietary inclusion of 25 to 50 mg/kg astaxanthin increased the activities of intestinal digestion and absorption enzymes (lipase, creatine kinase, and alkaline phosphatase), while the inclusion of 25 to 75 mg/kg astaxanthin improved the immune response of fish. Furthermore, regardless of inclusion level (25 to 125 mg/kg), dietary astaxanthin supplementation strengthened the intestinal mucosal barrier function and improved antioxidant activity, thereby promoting intestinal development. Conclusively, 25 to 75 mg/kg astaxanthin from WBHPA was recommended to be included in diets for rainbow trout.

Keywords: Antioxidant; Astaxanthin; Growth; Immune; Intestinal health.

Fig. 1

Regression analysis between dietary astaxanthin content (mg/kg) and weight gain (WG, %), feed conversion ratio (FCR) as well as hepatic malondialdehyde (MDA) content (mmol/mg protein) and catalase (CAT) activity (U/mg protein) in rainbow trout fed diets with various levels of astaxanthin from wall-broken Haematococcus pluvialis.

Fig. 2

Morphological structure of hindgut in rainbow trout fed diets with various levels of astaxanthin from wall-broken Haematococcus pluvialis (WBHPA). (A) Histological sections of rainbow trout fed with the (a) control, (b) WBHPA-25, (c) WBHPA-50, (d) WBHPA-75, (e) WBHPA-100, and (f) WBHPA-125 diet, respectively, with H&E staining. Scale bar, 400 μm. Magnification, 80×. (B) Intestinal morphology parameters (means ± SE).

Fig. 3

The relative expression (means ± SE) of (A) anti-inflammatory related genes in hindgut, (B) pro-inflammatory related genes in hindgut, (C) anti-inflammatory related genes in liver, and (D) pro-inflammatory related genes in liver of rainbow trout fed diets with various levels of astaxanthin from wall-broken Haematococcus pluvialis (WBHPA). pIgR = polymeric immunoglobulin receptor; IL = interleukin; TGF-β1 = transforming growth factor-beta 1; IFN-γ = interferon-gamma; TNF-α = tumor necrosis factor-alpha. ^a,b,cBars with different superscript letters differ significantly (P < 0.05).