2.3 challenge test
At the 4th week and 8th week of the feeding experiment, 10 shrimps from each replicate were injected intramusclarly with 5.0x10^7 cells/ml of V.harveyi bacterial stock solution (TSB supplemented with 30 mg mL-1 NaCl,Difco) at a dose of 20 มิวแอล per shrimp at the 4th week and and with 3.4x10^7 cell mL-1 of V.harveyi bacterial stock solution at a dose of 50มิวแอล per shrimp at the 8th week.