The Immunostimulatory Effects of Commercial Feed Additives on Growth Performance, Non-specific Immune Response, Antioxidants Assay, and Intestinal Morphometry of Nile tilapia, Oreochromis niloticus

Abstract

The main objective of the present research was to investigate the impacts of commercial immunostimulants on growth, non-specific immune response, antioxidant enzymes, and intestinal morphometry of Nile tilapia, <i>Oreochromis niloticus</i>. Fish (100 ± 6.5 g) were randomly divided into five groups in triplicates (150 fish in each replicate), stocked in 20 m² of aerated concrete ponds. The fish were fed on a control diet (30.0% crude protein) (control), and four experimental diets supplemented with Yeast Plus^®, Digestarom^®, and Biotronic^® Top³ at 1 kg ton^-1, and Sanolife PRO-F^® at 0.5 kg ton^-1. After the experimental period, the highest significant yield (kg m^-3), mean final weight (g fish^-1), average weight gain (g fish^-1), and specific growth rate (% body weight day^-1), were recorded in fish fed on the diet supplemented by Sanolife PRO-F, followed by Yeast Plus ponds. The lowest yield was recorded in the control group. However, the feed conversion ratio was significantly decreased with Sanolife PRO-F diet. Furthermore, the hematological analysis increased in the following ascending order: Sanolife PRO-F^®; Yeast Plus^®; Biotronic^® Top3 and finally Digestarom^® groups. The lowest concentrations of white blood cells, red blood cells, hematocrite, and hemoglobin (<i>P</i> ≤ 0.05) were observed in the control group. The levels of phagocytic activity and phagocytic index were significantly higher in fish fed with Sanolife PRO-F^® group (<i>P</i> ≤ 0.05). Likewise, serum lysozyme activity was significantly highest in Sanolife PRO-F (0.63 and 0.68 U/mL, after 0.5 min and 3 min, respectively). Levels of total serum proteins, globulin, Immunoglobulin M, catalase, and super oxide dismutase were significantly higher in fish fed with Sanolife PRO-F^® supplement. On the contrary, length measurement of the intestinal villus height/width, absorption area, crypt depth, and goblet cells, were significantly lower in the control group, whereas their highest values was observed in fish fed Sanolife PRO-F (<i>P</i> ≤ 0.05). Consequently, Sanolife PRO-F^® is recommended at a level of 0.5 kg ton^-1, to improve the growth performance, antioxidative capacity, and immune response of Nile tilapia.