Oxidative stress response of black tiger shrimp ( Penaeus monodon) to enrofloxacin and to culture system

In Vietnam, enrofloxacin is one of the most commonly used antibiotics in shrimp farms. Although the European Union set a maximum residue limit (MRL) of 100 μg/kg for enrofloxacin and its metabolite ciprofloxacin in edible tissues of aquatic animals for human consumption, only few data are available on its potential deleterious effects on shrimp. This study aimed to investigate the impacts of enrofloxacin on oxidative stress in hepatopancreas and gills of black tiger shrimp ( Penaeus monodon). Experiments were conducted under laboratory and field conditions, for which two different culture systems were distinguished (intensive and improved extensive culture systems). Shrimp (average weight of 10 g) were fed with medicated-feed containing 4 g enrofloxacin/kg for 7 days. We showed that enrofloxacin medication caused very small changes in oxidative stress status of the shrimp. However, the culture system has a significant impact. The basal level of hepatopancreas lipid peroxidation (LPO) was higher in intensive than in improved extensive culture system, while glutathione S-transferase (GST) activity was lower in the former system. In addition, an elevated gill catalase (CAT) activity was observed in the shrimp sampled from intensive culture. In conclusion, LPO, CAT and GST can be proposed as biomarkers to point out the general stress status of the shrimp and to discriminate between shrimp cultivated in intensive and improved extensive culture systems.