The study investigated effect of dietary supplementation with malic acid, Bacillus subtilis, and a mixture of the two (3 × 2 factorial trial) on the growth, feed utilization, stomach and gut pH, gut total count bacteria, and the hematological and biochemical blood parameters of Nile tilapia, Oreochromis niloticus. Treatment groups (T1 to T6) were fed diets (289.90 g kg-1 crude protein and 18.44 MJ kg-1 gross energy) containing three levels of malic acid (0.0, 5.0, and 10.0 g kg-1), each of which was supplemented with 0 and 1.1×105 cfu g-1B. subtilis, respectively. Each treatment group was assigned randomly to triplicate groups of 35 fish (5.26 ± 0.06 g) in 18 tanks for 84 days. The results indicated that survival was significantly higher in all dietary treatments in comparison with control group T1. The highest values of FBW, WG, and SGR (%), PER, PPV, and ER were recorded in groups T4 and T6, which were fed diets supplemented with 5 g malic acid kg-1 and 1.1×105 cfu g-1B. subtilis and 10 g malic acid kg-1 and 1.1×105 cfu g-1 B. subtilis, respectively. The best value of FCR was obtained in groups T4 and T6. The lowest total bacterial count in the gut and feces was detected in fish from group T6. The values of hematocrit, hemoglobin, red blood cells, total white blood cells, total protein, albumin, and globulin were significantly higher (P |
