Protective effects of Sargassum horneri against ammonia stress in juvenile black sea bream, Acanthopagrus schlegelii

Ammonia is an important environmental toxic pollutant that represents a biochemical and physiological hazard to living organisms, especially in intensive culture systems with high stocking density. This study aimed at evaluating the protective effects of Sargassum horneri (SH) on ammonia stress in black sea bream. Four hundred and eighty fingerlings with approximate mean body weight 12.0 ± 0.1 g were randomly distributed into four experimental groups in triplicate. Each group was stocked with 40 fish and fed with isonitrogenous (42% crude protein) and isolipid (12% crude lipid) experimental diets containing either 0% SH (control), 3% SH, 6% SH, or 9% SH in the feed. At the end of 8 weeks of experimental feeding, fish were exposed to ammonia for 24 h. The results indicated that ammonia stress led to an increase in oxidative stress as shown by elevation in the levels of cortisol and liver lipid peroxidative damage markers as well as decrease in antioxidant biomarkers. Furthermore, humoral immunity was suppressed during the stress period. However, fish supplied with S. horneri had significant improvement in immune response, antioxidant capacity, and resistance against ammonia stress, particularly in the 6% SH group. Therefore, dietary S. horneri supplementation at an optimum level of 6% could increase the resistance of juvenile black sea bream to ammonia-induced stress.