الفهرس 
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Abstract
The present study was carried out in Fish Nutrition Laboratory, National Institute of Oceanography and Fisheries (NIOF), Alexandria, Egypt. This research aimed to investigate the feasibility of reducing the fish meal (FM) ingredient, as far as possible, in European sea bass feeds by using either of two animal/aqua protein alternates (namely: fish-wasts or fermented fish-wastes) in order to lower cost and future reliance on FM. Additionally, the study aimed to evaluate the potentiality of using two feed acidifiers/organic salts, namely: sodium butyrate or sodium propionate as supplements for enhancement of growth and improvement of basal health status of fish. Three experiments or feeding trials were carried out in the current research, with juveniles or fry sea bass, and each has lasted for 90 days.
The 1st experiment:
”Fish meal-substitution with 2 fish-waste meals in sea bass juvenile’s diet”
Partial replacement of fishmeal (FM) by fish-wastes or fermented fish wastes (FW or FFW) in sea bass (" ~ "29 g) diets was evaluated by testing three levels of FM-substitution: 15%, 30% and 45% to determine the opimal substitution level.
The obtained results are summarized as follows
• Basically, a fish-waste meal (FW30 diet) appears to be an appropriate animal-protein source for substitution 30% of the FM ingredient in sea bass diet. However, higher FM-substitution level (45%) by either FW or FFW had caused reduced some growth criteria (WG & sGR).
• No negative effects (insignificant variations) are detected on feed utilization efficiency indices, namely: feed intake (FI), feed conversion ratio (FCR), protein efficiency ratio (PER) and protein productive value (PPV).
• No significant variations in the measured biometric indices: condition factor (K), hepatosomatic (HSI) and viscerosomatic (VSI) are detected among all dietary groups, except for relative gut length (RGL) which recorded the highest values for fish fed the FFW45 diet.
• Fish body composition showed significant variations among dietary treatments in lipids and moisture contents, however, protein, ash and whole fish amino acid profile remained unaltered.
• FW meal at 15 or 30% FM-replacement level improved basal health status of fish, many physiological parameters competence as compared to CTRL fish. However, the highest substitution level (45% of FM) in both FW and FFW treatments exhibited compromising reduction in all major blood constituents which is a strong indicator for a depressed health status.
• FW30 diet had a remarkable reduction influence on pathogenic bacteria, concomitant with an increase in the beneficial bacteria in fish distal intestine suggesting an improved gut-health functionality and immunity response as well.
• To sum up: 30% of fish meal in the diet of juvenile European sea bass can be replaced with FW meal without adverse effects on growth performance, feed utilization or general health status.