Probiotic Effects of Arthrobacter nicotianae and Bacillus cereus on the Growth, Health, and Microbiota of Red Tilapia (Oreochromis sp.)

Abstract

This study evaluated the effects of a commercial probiotic containing Arthrobacter nicotianae and Bacillus cereus on the growth performance, intestinal histological structure, body composition, hematology, and microbiota of red tilapia. Fingerlings were fed four different diets: a control diet (Pd0) and three diets (Pd1, Pd2, and Pd3) containing 15, 20, and 40 mL of probiotics/kg, respectively, for 12 weeks. Probiotic supplementation had no significant effect on water quality parameters. Compared with the control diet, all the probiotic diets improved growth performance, with greater final body weight (FBW), net weight gain (NWG), weight gain, average daily weight gain (ADWG), specific growth rate (SGR), and feed conversion efficiency (FCE). The feed conversion ratio (FCR) was lower in all probiotic-treated fish compared to control. The survival rate was also higher in the probiotic groups, though the difference was not significant. There was no significant difference in crude ash or lipid contents. However, protein content was significantly higher in Pd2 and Pd3, while moisture content (MC) was significantly higher in Pd3 than in the control group. Histological examination revealed increased villi length and width, being significantly higher in Pd2 and Pd3, while significantly greater muscular thickness and intestinal diameter were observed in Pd3-treated fish. These values increased with probiotic dose. The intestinal total viable count (TVC) was the highest in Pd2 and the lowest in the control group. The water TVC was the highest in Pd3 and the lowest in Pd0. The number of Bacillus spp. in the intestine and culture water increased with probiotic dose, while intestinal and culture water Vibrio counts decreased. Hematological analysis showed significant increases in red blood cell (RBC) count, hematocrit, mean corpuscular hemoglobin concentration (MCHC), and hemoglobin (Hb) in the treated groups compared with the control. The incorporation of A. nicotianae and B. cereus at 40 mL/kg in red tilapia diets improved growth performance, intestinal health, and general welfare.