KeywordsGrowth performance, Japanese quails, native lactobacilli, serum biochemical parameters. ABStRACtThe objective of the present study was to evaluate the probiotic effects of different concentrations of four selected native Lactobacillus strains on the growth performance and serum biochemical parameters of Japanese quails. A completely randomized design (CRD) was applied, including seven probiotic treatments with four replicates of 20 quails each, totaling 560 quails. Treatments were applied for five weeks. Four native Lactobacillus strains were anaerobically grown in a 10-L batch fermenter and lyophilized (10 10 CFU/g). Treatments were as follows: T1: control (basal diet); T2: commercial probiotic CP1; T3: commercial probiotic CP2; and T4, T5, T6, and T7: four native strains added at levels of 50, 100, 150, and 200 g/ton diet, respectively. The native probiotics significantly improved body weight gain (BWG) and feed conversion ratio (FCR) during the starter, finisher, and overall periods (35 days) (p<0.05), whereas no significant effect was observed on feed intake. The native strains significantly influenced the serum glucose, total protein, globulin, phosphorus, uric acid, low-density lipoprotein (LDL), LDL/HDL ratio, white blood cell counts (WBC), and mean corpuscular hemoglobin concentration (MCHC) of quails during the rearing period (p<0.05), whereas treatments had no influence (p>0.05) on blood cholesterol, calcium, high-density lipoprotein (HDL), or hemoglobin (HB) levels or on red blood cell counts (RBC). The cecal and small intestine samples of the quails fed the native Lactobacillus strains contained significantly higher Lactobacillus spp. and lower E. coli populations compared with the control diet and those supplemented with commercial probiotics. It was concluded that the use of the native Lactobacillus strains (150 g/ ton diet) promoted the best performance of Japanese quails.