Growth performance, hematological profile, and related genes expression in goldfish (Carassius auratus) fed on rosmarinic acid-enriched diets and subjected to ambient ammonia

Recently, supplementing fish diets with polyphenols has attracted more attention because of their great nutritional role. The unionized ammonia is one of the critical water parameters that adversely affects the fish performance and welfare status. Hence, the present perspective outlines the potential value of dietary rosmarinic acid (RA) in boosting growth, hematological, and immune biomarkers, besides related-genes expressions post-exposure of goldfish (Carassius auratus) to ambient ammonia. Fish (n = 240) were separated into four groups; RA0 (the control), RA400, RA600, and RA800 received 0, 400, 600, and 800 mg RA/kg feed, respectively. After 56 days, counts of white and red blood cells and growth indices (weight gain, specific growth rate, feed intake, and feed conversion ratio) were evaluated. After that, the fish per each treatment were exposed to 0.5 mg/L of unionized ammonia for three hours. After the challenging time, many biomarkers were measured including immune response (ACH50, total immunoglobulin, and lysozymes activity), digestion (proteases activity), and genes expression involving MUC, HSP27, HSP30, HSP47, TNFa, Lp1, and Fas genes plus the anti-inflammatory cytokines (IL6, IL8, and IL10). The findings of the current research revealed that dietary RA intervention fostered growth performance, improved blood picture (p < 0.05), and enhanced (p < 0.05) the expression of genes, which are responsible for modulating immunity and anti-inflammatory status in a dose-dependent manner. The present study concluded that dietary RA is a successful natural feed supplement for goldfish with an optimal level of 600 mg RA/kg feed. However, it verifies antitoxic and anti-inflammatory properties against ambient ammonia toxicity. It also has a promising influence on the growth, hematological, and immunity and anti-inflammatory related genes expression of goldfish, C. auratus.