الفهرس 
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Abstract
The present study was carried out at the laboratory of fish nutrition, Faculty of Agriculture, Benha University. The experiment started on 28 May 2012 and continued until 28 August of the same year (84 days). Results obtained from the present study could be summarized as follows:
Using solid-state fermentation (SSF) with Saccharomyces cerevisiae significantly (P<0.05) increased dry matter, crude protein, lipid and ash contents of soybean meal. Moreover, SSF with S. cerevisiae significantly decreased fiber content of yeast fermented soybean meal (YFSBM) while phytic acid and trypsin inhibitor were significantly decreased than commercial soybean meal (CSBM).
Essential amino acids, including arginine, histidine, lysine, methionine, leucine, isoleucine, threonine, phenylalanine and valine in FSBM increased by 8.39%, 2.72%, 30.95%, 14%, 30.10%, 4.19%, 2.25%, 4.25% and11.53%, respectively. Moreover, non-essential amino acid, glutamate, aspartate, serine, glycine, alanine, tyrosine, cystine and proline in FSBM increased by 24.94%, 16.86%, 0.46%, 11.05%, 10%, 25%, 65.22%, and 14.28%, respectively.
The highest BW, WG and SGR were recorded by fish fed the diet (25% fish meal (FM) replaced with YFSBM , D-25 and 50% fish meal replaced with YFSBM, D-50) with insignificant differences between the two groups.
The best feed conversion raio (FCR), the highest protein efficiency raio (PER) and protein productive value (PPV) recorded by fish were fed diets D-25 and D-50. The total replacement of FM with YFSBM led to a significantly (P<0.05) poor FCR ratio and lower PER (P<0.05) compared with the other experimental diets.
Apparent digestibility coefficient (ADC) for protein and lipid for fish fed the diet D-25 or D-50 were significantly (P<0.05) higher than that of the other experimental diets.
There were significant differences in body crude protein, crude lipid and ash content of fish fed the experimental diets (P<0.05). Body ash content tended to decrease as the level of protein replacement increased from 0 to 50%, while, body lipid had the opposite trend. However, all these parameters showed the opposite trends as protein content of FM replaced by FSBM increased from 50 to 75%.
No significant (P>0.05) difference was found in hematocrit (Htc), hemoglobin (Hb) and red blood cells (RBCs) among fish treated with all tested diets.
White blood cells (WBCs), albumin and globulin were significantly (P<0.05) higher in fish fed diets D-25 or D-50 in comparison to the other dietary groups.
Activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in blood serum significantly increased (P<0.05) in fish fed the control (D-0), D-75 or D-100 but, the lowest activities of ALT and AST recorded by fish fed the diets D-25 or D-50.
Creatinine level and uric acid content in blood significantly (P<0.05) increased in the control group than the other treatments.
Complement component (C3), growth hormone and insulin like growth factor (IGF1) significantly (P<0.05) increased with increasing YFSBM in the diet up to 25% or 50% replacement.
Calcium and potassium contents in blood were significantly (P<0.05) higher in fish fed the control diet, D-25 and D-50 and the differences between these treatments were not significant (P>0.0).
CONCLUSIONS
The present study concluded that:
• The nutritional value of soya bean could be improved by the solid-state fermentation by S. cerevisiae, as it increases the protein content and decreases tripsin inhibitor percent and Phytic acid content.
• Fishmeal could be replaced by yeast fermented soybean meal at level 50% without any significant effect on growth indices, feed utilization, blood properties and immunity properties of Nile tilapia (Oreochromis niloticus) fingerlings. In addition, it decreases the diet costs by 16.02% in comparison to control diet.