الفهرس 
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Abstract
This experiment was aimed to investigate the effect of dietary supplementation with exogenous enzymes such as phytase and protease enzymes on the growth performance, haemato-immunological, antioxidative status, and intestinal histomorphometry of European seabass (Dicentrarchus labrax).
This study was carried out on one hundred and fifty Sea bass (Dicentrarchus labrax) fingerlings with an initial body weight of 20 ± 2 g were obtained from Borg Al-Arab Alexandria Governorate, Egypt. The fingerlings were stocked into 15 fiberglass tanks (each with 30 m3) at the same. Each tank was stocked with 10 fish. Before the start of the experiment, fish were acclimated to the experimental conditions for two weeks, during this period fish were fed a control diet at 3% of body weight. The daily ration was divided into three equal amounts and offered three times a day (09:00, 1:00, and 3:00 pm). The fish were fed one of five experimental diets for 56 days (8 weeks). The fiberglass tanks were supplied with treated saltwater by sand and biological filters (30 ppt from the digging well) and fish were held under natural light
(12:12 light: dark schedule). During the experiment, water samples were collected to measure water quality.
Our study concluded that:
1. Effect of exogenous enzymes on growth and feed utilization
The present study proved that, dietary protease (1000 and 2000 mg/kg diet) improved the growth performance (FBW and WG) and feed nutrient efficiency (FCR) more than the supplementation of phytase (1000 and 2000 mg/kg diet) and control diets.
2-Effect of exogenous enzymes on hematological parameters cleared that, the higher level of RBCs, HB, HCT (%) and WBCs were recorded in the D5, D3, D4 respectively for 8th weeks. The highest level was noticed in D5, where the diet was supplemented with (Protease 2000 mg/kg diet). Also, the lymphocytes (%) and monocytes (%) increased in the following ascending order (D5), D3, D4, D2, and D1 were feed on a basal control diet, respectively.
3-The results cleared that, in general, the groups supplemented with a high dose of protease for 8th weeks is revealed the best results in the differential leucocytic count than the other groups as well as control groups.
4-Effect of exogenous enzymes on immunological parameters
The present study recorded that, the phagocytic activity and phagocytic index, serum total proteins, and globulin were significantly elevated in the groups supplemented with a high dose of protease (2000 gm/Kg diet) for 8th weeks than the other groups and control.
5-Our results cleared also, that, conversely, the values of (S.AST) and (S.ALT) were significantly lowered in groups fed diets supplemented with high levels of each of phytase and protease and also lower than the control group at the end of the experiment.
6-There is a decrease in antioxidants enzyme (CAT and SOD) in the serum of sea bass after supplementation of high levels of both phytase and protease than the control group for 8th weeks. Conversely, results revealed that there is an increase in antioxidants enzyme (LPO) in the serum of sea bass after supplementation of high levels of both phytase and protease than the control group for 8th weeks.
7-Effect of exogenous enzymes on the intestinal morphometry, the study cleared that, the supplementation of phytase and protease increased the villus height and villus width of intestinal mucosa of sea bass for 8th weeks.