Efficacy of the dietary Malva parviflora leaves in modulating immune-antioxidant functions, resistance to Candida albicans and Streptococcus agalactiae infection, digestive/absorptive capacity, and growth of Nile tilapia (Oreochromis niloticus)

Recently, the intervention of herbal plants in the fish diet has drawn a lot of interest due to their unique nutritional value and pharmacological properties. To assess the impact of dietary incorporation of Egyptian mallow, Malva parviflora leaves powder (MPLP), a 10-week feeding trial was carried out on Nile tilapia (Oreochromis niloticus). The assessment encompassed the effects on growth, digestive/absorptive efficiency, biochemical, and immuno-antioxidant responses. Four treatments containing a total of 200 fish (n = 50 fish/treatment; five replicates/treatment; 10 fish/replicate) with an average weight of 37.50 +/- 0.22 g (means +/- SE) were randomly assigned. The MPLP was added to the basal diet at 0 (control diet, MPLP0), 5 (MPLP5), 10 (MPLP10), and 15 (MPLP15) g/kg diet concentrations and served to the fish for 10 weeks. After the trial, the fish were exposed to pathogenic yeast (Candida albicans) and bacterium (Streptococcus agalactiae) infection. Results displayed that MPLP-incorporated diets significantly (P < 0.05) enhanced the growth, intestinal digestive enzymes (amylase and lipase), and intestinal morphometrics (villous length and width and goblet cell count). The increases were in a level-dependent way, and the MPLP15 diet showed the highest values. Dietary MPLP notably (P < 0.05) enhanced growth hormone and declined leptin hormone, glucose, and cholesterol levels. Moreover, the immunological (serum bactericidal activity, myeloperoxidase, and complement 3) and antioxidant (catalase, glutathione peroxidase, and total antioxidant capacity) biomarkers were augmented in the MPLP-fed groups in a level-dependent way (P < 0.05). Fifteen days post-infection with C. albicans and S. agalactiae, the survival rates among the infected fish enhanced as dietary MPLP levels rose; the MPLP15 group had the highest survival rates (90.91 and 81.82%), respectively. Overall, dietary MPLP intervention can boost the growth, digestive capacity, disease resistance, and immune-antioxidant status of Nile tilapia. These positive effects may contribute to a sustainable aquaculture industry.