الفهرس 
1. Introduction and aim of the workOnly 14 pages are availabe for public view
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Abstract
The present study is carried out at the laboratory of fish nutrition, Faculty of Agriculture, Banha University. The experiment started on 20 June 2020 and continued until 20 September of the same year.
A 2×3 factorial experiment was designed to study the effect of different dietary protein levels suboptimum level (25%) and optimum level (35%) and different zinc oxide (ZnO) forms, Bulk zinc oxide (BZnO) or Nano zinc oxide (NZnO) and their interaction on growth promotion, feed utilization, endogenous intestinal enzymes, hematology, serum biochemical, antioxidant and immune responses, and related gene expression of Nile tilapia.
The experimental design was outlined as follows:
T1 25% dietary protein levels with Normal Zn in diet ingredients
T2 25% dietary protein levels supplemented with 60 mg BZnO kg-1 diet.
T3 25% dietary protein levels supplemented with 60 mg NZnO kg-1 diet.
T4 35% dietary protein levels with normal level of ZnO
T5 35% dietary protein levels supplemented with 60 mg BZnO kg-1 diet.
T6 35% dietary protein levels supplemented with 60 mg NZnO kg-1 diet.
A set of 360 fish of Nile tilapia, mono-sex male fingerlings with an average initial weight of 7.53 ± 0. 06 g, were used in this experiment. Twenty fish were randomly stocked into each cylindrical fiberglass tank with triplicates for each treatment. During the experimental period, all groups of fish were hand-fed with their respective diet divided into three equal amounts and offered three times a day at 09:00 am, 12:00 pm and 03:00 pm, at a rate of 5% of biomass. Fish were taken from each tank, weighed and the amount of feed was adjusted (every two weeks) according to the changes in body weight through the experimental period. Feed intake was calculated and expressed as the total feed intake in whole period of experiment per fish.
Results obtained from the experiment are summarized as follows:
The highest FBW, WG and SGR were recorded by fish fed diet containing 35% crude protein and supplemented with NZnO form. No significant (P > 0.05) differences in FBW, WG and SGR between fish fed diet containing 35 % crude protein without Zn supplementation and fish fed diet containing 25 % crude protein supplemented with NZnO form.
The best FCR was recorded by fish fed diet containing 35% crude protein and supplemented with BZnO form. No significant (P > 0.05) differences in FCR and PER between fish fed diet containing 35 % crude protein without Zn supplementation and fish fed diet containing 25 % crude protein supplemented with NZnO form.
The lowest value of RIL was obtained by in fish fed diet containing protein level 25% and supplemented with BZnO form.
The lowest HSI value was recorded in diet containing protein level 35% and supplemented with NZnO.
The highest Hb value was obtained by fish fed diet containing protein level 35% and supplemented with NZnO.
The highest value of Hct was obtained by fish fed diet containing protein level 35% and supplemented with BZnO or NZnO.