Dietary α‐Ketoglutarate supplementation alleviates harmful effects of high environmental ammonia on grass carp,Ctenopharyngodon idella

Abstract

Current intensive fish farming usually causes high environmental ammonia (HEA) in ponds that is toxic to fish. α-Ketoglutarate (α-KG) can be rapidly transaminated to glutamic acid and further aminated to glutamine. Therefore, we hypothesized that dietary α-KG supplementation would alleviate HEA toxicity to fish. To test the hypothesis, 270 healthy grass carp (Ctenopharyngodon idella) juveniles were randomly assigned to control, HEA (18.37 mg/L ammonia) and HEA + α-KG (0.75% of α-KG) groups. Ammonia and free amino acid content in plasma and brain, liver glutamic pyruvic transaminase and glutamic oxaloacetic transaminase activity, and urea and glycogen content were measured on the first, seventh and 42nd days. Our results showed short-term HEA exposure (1 day) led to a significant ammonia accumulation in the brain and plasma and significantly decreased glutamic and aspartic acid content in the brain and increased glutamine content in the brain and plasma. The long-term HEA exposure (42 days) caused significant reductions in glycine and arginine content in the brain tissue. In most cases, dietary α-KG supplementation alleviated the fluctuations in FAA content in the brain and plasma. Our results suggested dietary α-KG alleviated HEA toxicity to grass carp.