Effect of AquaVacTM VibromaxTM on size and health of post larva stage of Pacific White shrimp Litopenaeus vannamei and Black Tiger shrimp Penaeus monodon

This study was conducted to evaluate the efficacy of AquaVac™ Vibromax™, an inactivated Vibrio bacterin product, to promote health and resistance to vibriosis in penaeid shrimp post larva (PL). Black Tiger shrimp (Penaeus monodon) and Pacific White shrimp (Litopenaeus vannamei) were fed ad libitum with VibromaxTM- enriched Artemia for 10 consecutive days, PL5-PL14. Artemia nauplii were enriched by incubating 150g Artemia nauplii in 1L VibromaxTM for 1.5h prior to feeding. Varying dosages; half, single and two times overdose were compared for their effectiveness. A control group was fed on normal (non-enriched) Artemia. Shrimp PLs were challenged with a single immersion bath of 1.0-1.4×10⁵ CFU/ml Vibrio parahaemolyticus on day one (PL15) or day seven (PL21) following the 10day feeding treatment to test their disease resistance, and the survival rates amongst groups were compared. Shrimp PLs were observed for their growth (body wet weight and length) and survival over the experiment until PL23. Histological preparation of the hepatopancreas and other visceral organs were examined for general health condition of the shrimp PLs. The body wet weight and length of shrimp PLs following a 10day feeding trial indicated that the use of VibromaxTM promoted growth in both Black Tiger shrimp (average length and weight in treated groups at PL23: 1.77±0.08cm and 26.84±2.50mg; length and weight in control group at PL23: 1.72±0.19cm and 22.11±7.19mg) and Pacific White shrimp PLs (average length and weight in treated groups at PL23: 1.71±0.01cm and 31.82±2.85mg; length and weight in control group at PL23: 1.46±0.37cm and 23.08±12.95mg). The health promoting effect of VibromaxTM was also supported by the higher survival of PL23 in Black Tiger Shrimp from the treatment groups (average Relative Percent Survival: 52 %, 72 %, and 48 % for half dose, single dose, and two times overdose, respectively). Histological examination of hepatopancreatic tissue from the treated PLs did not demonstrate any adverse effect of the treatments. Although hepatopancreatic inclusion bodies, indicating pathological signs of monodon baculo virus (MBV) infection, were observed in certain populations of Pacific White shrimp PLs, the PLs that received the feeding treatment generally demonstrated better growth and survival than those of the control group. Overall results from the present study support the health promoting effect of Vibromax™ on growth and survival of shrimp PLs. The efficiency varied according to the dosage of VibromaxTM administered and pre-existing health condition of the PL.