Before challenge, 10 shrimps were randomly chosen from each family for confirming the absence of WSSV. Shrimps (n=120) with 7.23–8.15 g of body weight were randomly chosen from each family (G2–G5) and maintained in aquaria for 7 d, fed with approximately 0.23–0.40 g (3%–5% of shrimp weight) of commercial feed daily.