The aquaculture industry is facing considerable challenges due to spatial limitations and rising demand for food fish, resulting in the need to increase production through vertical expansion by increasing stocking densities within existing rearing facilities. However, this approach has resulted in increased competition for resources and crowding stress among fish, adversely affecting their growth and immune responses. Research indicates that dietary supplementation with phytogenic compounds, organic acids, probiotics, vitamins, etc., can mitigate stress effects in fish. Despite extensive studies on the influence of phytogenic substances and organic acids on fish health and performance, there remains a notable gap in knowledge regarding the impact of acidified phytogenic agents on fish. To investigate this, a sixty-day feeding trial was conducted to evaluate the growth and immuno-physiological effects of Ixora coccinea (IC) either alone or in combination with 0.2% sodium propionate (SP) in the diets of Nile tilapia.
Five distinct diets were formulated: control, 0.1% IC, 0.2% IC, 0.1% IC + SP (0.2%), and 0.2% IC + SP (0.2%). Two hundred twenty-five fingerlings, averaging 6.69 g ± 0.01, were randomly distributed across fifteen tanks for the trial. The findings revealed that dietary supplementation with IC, either alone or in combination with SP, did not significantly affect growth performance. However, there was a notable increase in neutrophil and lymphocyte counts among fish fed IC- or IC-0.2% + SP and IC-0.1%, respectively, compared with the control group (p < 0.05). While no significant variations were observed in red blood cell (RBC), white blood cell (WBC), and hemoglobin (Hb) counts, there was an increase in the activities of superoxide dismutase (SOD) and catalase (CAT) enzymes in the IC- and IC+SP-fed groups, respectively (p < 0.05). Furthermore, fish fed the IC-0.1% + SP and IC-0.2% + SP diets exhibited elevated levels of total immunoglobulin (Ig) and total protein compared to the control (p < 0.05). In conclusion, the supplementation of IC powder, either alone or in combination with SP, positively influenced immuno-physiological parameters and stimulated CAT enzyme activity without adversely affecting growth performance.