Exogenous nucleotide supplementation during times of rapid growth and stress is preferred because de novo synthesis is insufficient and energetically a costly process. To overcome inefficient utilization of dietary nucleotides due to intestinal cell repulsion and dependency on pH, an efficient controlled delivery system based on chitosan nanoparticles (NPs) was developed. The effects of these (0.2% and 0.4%) RNA-loaded chitosan NPs (Chitosan: RNA ratio 2:1, 0.4% bare RNA, 0.8% chitosan NPs on productive efficiency (growth rate, feed conversion and protein efficiency ratio), body composition, organo-somatic indices, haemato-biochemical and immune responses (WBC count, phagocytic activity, serum lysozyme, serum total protein and albumin: globulin ratio) and survival of Labeo rohita fish fingerlings, following challenge with pathogenic bacteria were evaluated. Dietary chitosan NPs were found not to affect productive efficiency, but improved (P < 0.01) immunity by increasing WBC and phagocytic activity. Dietary RNA significantly improved (P < 0.01) productive efficiency, immunity and survival, which was further potentiated (P < 0.01) by its nano-sized delivery by loading onto chitosan NPs. Blood glucose, haemoglobin, RBC count, serum uric acid and whole body composition were unaffected (P > 0.05) by dietary treatments. RNA-loaded chitosan NPs increased hepato- and viscero-somatic indices. The activity of metabolic enzymes (intestinal and liver alkaline phosphatase, alanine- and aspartate-amino transferases, lactate- and malate-dehydrogeneases) corresponded with the performance of the respective diets. As growth, immunity and disease resistance in fish given dietary nano-sized RNA were significantly higher than in those given bare RNA or chitosan alone, and as nanoformulation reduced the usage of individual components by half, the use of RNA-loaded chitosan NPs can be favoured in the feed/food industry over chitosan and RNA alone.
Central Institute of Fisheries Education, Versova, Mumbai 400061, India.