A review of dietary approaches for ammonia toxicity remediation in fish

We reviewed available data regarding the benefits of feed additives for mitigation of ammonia toxicity in fish. We first emphasized the toxic effects of ammonia and the pathways involved in ammonia metabolism in fish. Then, we focused on the roles of different dietary additives on internal ammonia detoxification and/or to counteract the negative effects of ammonia toxicity. A wide range of feed additives has been studied for their benefits in fish under ammonia exposure. Most of these studies focused on the improvement of fish health and growth performance by these additives, but neglected underlying mechanisms of these effects as well as ammonia detoxification. It is necessary to monitor internal ammonia, urea, amino acids levels, ammonia/urea excretion, and enzymes involved in ureagenesis and glutamine formation along with health-related parameters (e.g., antioxidant, immunological, and growth responses) in the future studies to fulfil the knowledge gap. Moreover, the future researches should consider the route of ammonia and supplements administration to obtain reliable and practical data. A little evidence shows that dietary nutrients may interact to change the results of dietary supplementation on ammonia toxicity remediation, which must be considered in the future studies.