Abstract:
Synbiotics, a synergistic combination of probiotics and prebiotics, are now highlighted as one of the most practical nutritional supplements in red tilapia farms. The aim of the present study was to assess the effect of the dietary inclusion of Jerusalem artichoke, Lactobacillus rhamnosus, or their combination, on serum biochemical, growth performance, intestinal morphology, immune parameters, intestinal bacterial count and protection against Aeromonas veronii in juvenile red tilapia (Oreochromis spp.). One hundred and eighty male red tilapias (average body weight of 14.05±0.42 g) were distributed into six 1000-liter tanks containing water under continuous aeration and an average temperature of 25–28°C. Tilapias were fed a basal diet (control, C), a 5.0 g kg⁻¹ Jerusalem artichoke-supplemented diet (5K), a 10.0 g kg⁻¹ Jerusalem artichoke-supplemented diet (10K), a 10⁸ CFU g⁻¹ LGG-supplemented diet (LGG), a 5.0 g kg−1 Jerusalem artichoke +10⁸ CFU g⁻¹ LGG-supplemented diet (5K+LGG), and a 10.0 g kg⁻¹ Jerusalem artichoke +10⁸ CFU g⁻¹ LGG-supplemented diet (10K+LGG) for 4 weeks. At the end of the feeding period, blood chemical, the growth performance, intestinal morphology, immune parameters, and intestinal bacterial count were analyzed. Then, fish from each diet were intraperitoneal-injected with 10⁷ CFU/fish of Aeromonas veronii. The results showed that the synbiotic-supplemented diet increased the total cholesterol and total protein levels of red tilapia. The WG, SGR, and ADG of fish fed with the 5K + LGG, 10K + LGG, LGG, 5K, and 10K diets were significantly (P < 0.05) higher than that fish fed the control diet. The absorptive area of the proximal and distal intestine of fish fed 10K+LGG was significantly higher (P < 0.05) than those fed the probiotic-supplemented diets (LGG), the prebiotic-supplemented diets (5K and 10K) and the control diet. The goblet cell counts showed that the numbers of acid mucous cells and double-staining mucous cells of the fish fed the synbiotic-supplemented diet (5K+LGG) in the proximal intestine were significantly higher (P < 0.05) than those of fish fed other diets. Moreover the results found that the fish fed the synbiotic-supplemented diets (5K+LGG and 10K+LGG) showed the numbers of acid mucous cells, neutral mucous cells and double-staining mucous cells in the distal intestine were significantly higher (P < 0.05) than those of fish fed other diets. The fish fed with the synbiotic-supplemented diets (5K + LGG and 10K + LGG) experienced a significant increase (P < 0.05) in the lysozyme activity and the number of probiotic bacteria in comparison with other groups. The cumulative mortalities of fish fed the synbiotic-supplemented diets (5K+LGG, 10K+LGG) were significantly lower (P < 0.05) than those of fish fed C, 5K, 10K, and LGG. Results suggested that Jerusalem artichoke and LGG-supplemented diets had the beneficial effect on serum biochemical, growth performance, intestinal morphology, immune parameters, intestinal bacterial count and protection against Aeromonas veronii in juvenile red tilapia (Oreochromis spp.).
