Effect of dietary supplementation of inulin and vitamin C on the growth, hematology, innate immunity, and resistance of Nile tilapia (Oreochromis niloticus) Mai D. Ibrahem a, * , Mohamed Fathi b , Salah Mesalhy d , A.M. Abd El-Aty c, ** a Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Cairo University,12211 Giza, Egypt b The World Fish Center, Regional Research Center for Africa & West Asia, Abbassa, Sharkia, Egypt c Department of Pharmacology, Faculty of Veterinary Medicine, Cairo University,12211 Giza, Egypt d Department of Pathology, Faculty of Veterinary Medicine, Suez Canal University, Egypt article info Article history: Received 1 December 2009 Received in revised form 9 March 2010 Accepted 26 March 2010 Available online 3 April 2010 Keywords: Inulin Vitamin C Oreochromis niloticus Innate immunity Growth Survival Challenge abstract The in vivo activities of inulin and ascorbic acid were evaluated experimentally via using 450 Nile tilapia (Oreochromis niloticus) that were distributed into 3 equal groups (each of three replicates). Fish of the first group served as a control and received a balanced diet free from inulin and vitamin C. The second fed on balanced diet supplemented with inulin (5 g kg 1 ), whereas, the third one received a balanced diet sup- plemented with vitamin C (500 mg kg 1 ). The survival and growth performances were evaluated. Blood samples were collected from the experimented tilapia, one and two months from the onset of the experiment to measure the hematocrit (HCT) values, nitroblue tetrazolium (NBT), and lysozyme activity. The protective effect of the two compounds was evaluated via challenge infection using pathogenic Aer- omonas hydrophila. The body weight gain (g); specific growth rate (%), and survival (%) were significantly increased (p < 0.05) in group supplemented with inulin and vitamin C after one and two months of exposures vs. the control. The HCT values showed non-significant changes in both supplemented groups after one and two months. The NBT was significantly increased (p < 0.05) in the 3rd and 2nd group after one and two months, respectively. On the other hand, a significant increase (p < 0.05) in the lysozyme activity has been observed in the 3rd group and in both supplemented groups at 1 and 2 months; respectively. The challenge infection showed an improved relative level of protection (RLP) in the 2 supplemented groups vs. the control. These results suggest that vitamin C at dose rate of 500 mg for one month could be a potential, less expensive, and promising dietary supplementation than inulin that would positively affect growth, hematology, innate immunity, and resistance of Nile tilapia (O. niloticus) in aquaculture. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Fish is one of the cheapest and promising sources of animal production; people can easily digest 93.2% and 93.7% of fish protein and fat, respectively [1]. Feed formulations accounts for more than 0.50 of the total production costs in modern intensive aquaculture. Increasing feed efficiency, especially by improving the metabolic assimilation of dietary nutrients, is of high priority in contemporary animal production. Any reduction in feed costs would have a direct positive effect on profitability of aquaculture [2,3]. Disease outbreaks were recently identified as the major constraint to aquaculture production with consequent adverse effects on the industry’s economic development [4]. The Motile Aeromonas Septicemia (MAS), caused by Aeromonas hydrophila, is among the dangerous infectious diseases that encounter in the majority of the freshwater fish culture [5e8]. Thus far, conventional approaches were used to control fish diseases, such as antimicro- bial agents and vaccination, however, they have had limited success in the prevention and/or treatment of aquatic diseases [9]. In addition to their public health hazards, the chemotherapeutic agents exert an ecological threat; because they increase the selec- tive pressure on the microbial world thus encourage the emergence of bacterial resistance [10,11]. Therefore, looking for less harmful approaches and more environmentally-friendly treatments become of premium importance. The concept of functional feed is novel to the aquaculture industry. It represents an emerging new paradigm to develop diets * Corresponding author. Tel.: þ20 2 33800575; fax: þ20 2 35725240. ** Corresponding author. Tel.: þ20 2 27548926; fax: þ20 2 35725240. E-mail addresses: mai_ibrahim12@yahoo.com (M.D. Ibrahem), abdelaty44@ hotmail.com (A.M. Abd El-Aty). Contents lists available at ScienceDirect Fish & Shellfish Immunology journal homepage: www.elsevier.com/locate/fsi 1050-4648/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.fsi.2010.03.004 Fish & Shellfish Immunology 29 (2010) 241e246