The use of phytobiotic substances as feed supplements in the aquaculture industry is generally increasing because of their safe and positive roles in promoting the performance, antioxidant, and immune responses of several aquatic organisms. In the current study, the stimulatory effects of dietary chia (Salvia hispanica) seed powder (CSP) on growth performance, antioxidant-immune responses, and disease resistance were evaluated in Nile tilapia (Oreochromis niloticus). For this purpose, six experimental diets were formulated to contain 0.0 g (control), 2.5 g, 5.0 g, 10.0 g, 15.0 g, and 20.0 g CSP/kg diet. Fish (9.2–10.6 g) were fed on the experimental diets up to satiety three times daily for eight weeks. Compared with the control group, CSP-fed fish showed higher growth performance particularly at treatments of 5–20 g/kg diet. Conversely, no significant changes were observed in carcass proximate composition (on fresh weight basis) among different CSP-fed fish groups. Feeding fish with CSP-enriched diets also boosted the hematological, hepatic antioxidant, and blood immune indices. Moreover, histomorphometry and absorption area of the intestine of CSP-fed Nile tilapia were linearly and quadratically enhanced when compared to the control group. Cell proliferation estimated by PCNA immunohistochemistry indicated that feeding fish on a 10.0-20.0 g CSP/kg diet showed lowest cell proliferation in liver and intestine tissues. It was also noted that the sera of CSP-fed Nile tilapia showed bactericidal activity against Aeromonas hydrophila, A. veronii, and Streptococcus iniae, and their maximum antibacterial activity were observed at the treatment of 20 g CSP/kg feed. Study results herein evoked that the dietary CSP; particularly at 10 g/kg feed, promoted the performance and disease resistance in Nile tilapia via enhancing its antioxidant and immune biomarkers. |
