ARTICLE FEED & ADDITIVE MAGAZINE January 2023 61 About S. R. Gokulnath S R. Gokulnath is a fisheries science graduate (B.F.Sc) of Tamil Nadu Dr J Jayalalithaa Fisheries University (TNJFU), Nagapattinam and have completed his Master’s degree program in Fish Nutrition and Feed Technology discipline at Kerala University for Fisheries and Ocean Studies, Kerala. His masters’s work was ‘Effects of alpha ketoglutarate on growth, antioxidant capacity, gene expression and amino acid profile in Nile tilapia (Oreochromis niloticus) fed with different level of protein diets’. He is an awardee of 'National Talent Scholarship' (NTS) of ICAR. About Phibi Philip Naduvathu Phibi Philip Naduvathu is a fisheries science graduate (B.F.Sc) of Tamil Nadu Dr J Jayalalithaa Fisheries University, Nagapattinam and Post-Graduate (M.F.Sc) of Central Institute of Fisheries Education (CIFE), Mumbai. His expertise is in fish genetics & biotechnology, aquaculture, fisheries & computational biology. Fish nutrition, aquatic ecology & conservation, climate change & AI are his extended interests. He is an awardee of prestigious 'Commonwealth Scholarship' by the UK government, 'National Talent Scholarship' (NTS) of ICAR and Institutional Scholarship of CIFE. About Dr. Chiranjiv Pradhan Dr. Chiranjiv Pradhan is a Bio-chemistry graduate with a doctoral degree in Fish Nutrition. His expertise is in bio-chemistry, fish nutrition, feed formulation, aquaculture, and animal health management. pu mirror carp after A. hydrophila injection. Also, Xu et al., (2017) stated that dietary AKG had positive effect on the lysozyme and neutrophil oxidative radical production. These findings suggest the use of AKG as an immunotherapeutic drug with potential advantages in the ability to fend against infection by harmful microorganisms in aquaculture. 5. Ammonia toxicity to amino acids Ammonia is a natural metabolite and plays an important role in maintaining the acid–base metabolic balance in the body. But ammonia toxicity has become one of the most common problems for aquatic animals, especially fish. As a final product of protein catabolism in most teleosts, ammonia is produced and excreted into the surrounding environment through the gills. Ammonium levels can rapidly rise to unsafe levels in aquatic systems unless the substance is continuously removed, usually by biological filtration or periodical water change. AKG is considered as a crucial molecule in transmembrane amino acid transport, protein metabolism, and cellular redox regulation. Dietary supplementation of AKG will increase the activity of glutamine synthetase (GS) enzyme which plays an important role in nitrogen metabolism (amino acid production) and reduces the toxicity of ammonium in the fish body. As the numbers of studies on Rh genes in animals have increased, the important roles of Rh glycoproteins in ammonia transport processes of aquatic animals have been confirmed. AKG up-regulates the expressions of Rhag and Rhbg genes, which promote ammonia excretion. In Atlantic salmon a 5.0 % AKG supplement reduced the nitrogen excretion without any negative effects on growth or vitellogenin synthesis. A study of Wang et al., (2016) showed that the concentrations of arginine, aspartate, glutamate, glutamine, and the total amino acids were increased by the addition of AKG, which are important amino acids for animals. These amino acids can also improve the growth of fish. CONCLUSION The primary goal of aquaculture scientists nowadays is to discover a vital supplement for improving the growth performance of fish. AKG has been a promising ingredient in aquaculture due to its multiple crucial functions even in molecular level. Adding an appropriate amount of AKG to the feed could increase the growth & immune performances of fish by reducing the feed conversion ratio, feed coefficient, promoting the metabolism of protein and fat in the fish, antioxidant capacity and digestive enzyme activity. The supplementation level of AKG shows species specific and feed protein level variations. But as far as the latest research findings, 0.75% and 1.0% of AKG supplementation showed promising results in aquaculture. There is still more to explore the molecular level activities of AKG and its effect in fish nutrition and physiology.
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