الفهرس 
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Abstract
This work was performed to clarify the effect of different dietary enzyme mixtures supplementation on growth performance, nutrient digestibility, immune response, some blood parameters and carcass traits of growing rabbits.
A total number of 55 New Zealand White rabbits (5 weeks old) were randomly divided into 5 experimental groups (11rabbit /group) ,and the average initial body weight of all groups was almost equal. The first group was kept as a control group and fed the basal diet without any supplementation, while the rabbits of the 2nd and 3rd groups were fed the basal diet supplemented with Superzyme at the rate of 0.25g and 0.5g/kg feed.respectively, while the rabbits of the4th and 5th groups were fed the basal diet supplemented with Natuzyme at a rate of 0.35 g and 0. 5 g /kg feed, respectively. The experimental period lasted for continuous 9 weeks. The obtained results are summarized in the following:
• Enzyme supplementation (groups 2 -5) of growing rabbit diets non significantly improved final body weight by about 10.09% and 12.3% 7.2% and 9.9% respectively when compared with the control.
• Enzyme supplementation improved final weight uniformity of rabbit when compared with the control.
• Enzyme mixture with sodium butyrate supplementation (groups 2 and 3) and higher level of enzyme mixture only (group 5) significantly increased total body gain throughout the whole experimental period by about 15.81%, 17.88% and 15.61% respectively, while lower level of Natuzyme (group 4) non significantly improved weight gain by about 11.4% when compared with the control.
• Enzyme supplementation (groups 2 -5) increased daily feed intake by about 19.4%, 20.5%, 23.6% and 21.2% respectively when compared with the control.
• Enzyme supplementation non significantly deteriorate FCR, PER by about (3.8%, 2.1% ,14.2and4.4%), (5.6%, 4.6% ,12.4and 7.4%) respectively and non significantly increase EEU by about (1.4%, .076% ,12.4and 4.07%) respectively of growing rabbits when compared with the control.
• It was observed that enzyme supplementation (groups 2 – 5) non significantly improved performance index of growing rabbits by about 20.01%, 22.9%, 10.69% and 18.19% respectively when compared with the control.
• Enzyme supplementation had no significant effect on blood serum total protein, albumin, globulin and glucose concentrations, while decreased (P≤0.05) blood serum total glycerides and cholesterol concentration when compared with the control.
• Enzyme supplementation reduced blood serum creatnine, uric acid, GPT and GOT concentrations when compared with the control. While had no significant effect on blood serum urea and alkaline phosphatase concentrations.
• Statistical analysis of the obtained data revealed that decreased total WBCs count by about 22.7%, 12.5%, 7.1% and 16.9% respectively when compared with the control.
• Enzyme mixture with sodium butyrate or alone supplementation (groups 2 – 5) non significantly increased granulocytes (esinophil, basophil and neutrophil) percentage by about 3.8% and 2.7%, 2.6% and 1.5% respectively when compared with the control. Moreover, it was observed that enzyme mixture with butyrate supplementation (groups 2 and 3) and higher supplementation level of enzyme mixture only (group 5) increased lymphocytes% by about 7.6%, 7.6% and 0.9% respectively, while lower supplementation level of enzyme mixture (natuzyme) reduced lymphocytes % by about 3.8% when compared with the control.
• Enzyme supplementation improved immune response of growing rabbits through improvement in phagocytic index and spleen relative weight.
• It was observed that enzyme mixture plus sodium butyrate and methionine supplementation at 0.25 or 0.5 g/kg diet (groups 2 and 3) respectively non significantly improved dry matter (DM), crude fiber (CF) and nitrogen free extract (NFE) digestibility by about (3.4% and 2.02%), (11.04% and 9.7%) and (4.5% and 5.8%) respectively when compared with the control, while reduced (P≥0.05) crude protein (CP) digestibility by about 2.75% & 8.1%. Moreover lower supplementation level (group 2) significantly improved (P≤0.05) ether extract (EE) digestibility by about 23.4%, but higher level (group 3) improved (≥0.05) EE digestibility by about 3.3% when compared with the control.
• On the other hand enzyme mixture supplementation only (groups 3 and 4) non significantly improved (P≥0.05) DM, CP, EE, CF and NFE digestibility by about (8.06% and 14.5%), (22.7% and 0.0), (5.9% and 3.7%), (39.4% and 220%) and (10.7% and 18.5%) respectively when compared with the control.
• Regarding dressing percent, it was observed that enzyme supplementation (groups 2 – 5) non significantly improved dressing percent of growing rabbits by about 6.2%, 6.6%, 7.0% and 9.2% respectively when compared with the control.
• Statistical analysis of the obtained data revealed that exogenous enzymes supplementation (groups 2 – 5) had no significant effect on kidney weight, heart relative weights, body skin relative weight, head before and after dressing relative weights and lung weight when compared with the control. On the other hand it was observed that enzyme supplementation decreased liver relative weight when compared with the control.
• The obtained data indicated that superzyme supplementation showed slight increase of villus length and hyperplasia of submucosal gland and bruners gland when compared with the control. On the other hand natuzyme (enzyme mixture) supplementation (group 4 and 5) showed moderate hyperplasia of bruners glandand increase the length of the intestinal villi.
• Enzyme mixture containing sodium butyrate or enzyme mixture only (groups 2 -5) to the basal diet improved economical efficiency of rabbit production (21.49, 23,56, 16.75 and 11.99) respectively when compared with the rabbits group fed on the basal diet without enzyme supplementation (4.23). The reason for that may be due to higher body gain.