الفهرس 
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Abstract
An experiment was carried out at the Rabbit Research Unit, Agricultural Researches and Experiments Station, Faculty of Agriculture, Mansoura University, during the period from March to April, 2015. The chemical analyses of the tested materials and the experimental diets were undertaken at the Laboratory of Poultry Production Department, Faculty of Agriculture, Mansoura University, Egypt. The objective of the present study was to evaluate the effects of feeding three dietary levels (0.0, 20 and 30%) of dried sugar beet tops with or without a prebiotic on the growth performance, digestibility of nutrients, carcass traits, certain blood plasma constituents, cecal characteristics and histological characterization of liver, ileum and cecum of New Zealand White (NZW) rabbits from 6 to 12 weeks of age. The most important obtained results can be summarized as follows: ∆ Replacing dietary alfalfa hay with SBT produced positive effects on growth performance of rabbits although feed intake was higher than that of the control group, irrespective of the added prebiotic. ∆ Digestibility coefficients of DM, OM, CP, EE and NFE of 12 weeks old NZW rabbits were positively affected by feeding the SBT-containing diets (20 % and 30%) compared with their control group. ∆ Dietary SBT level had no significant effect on pH value, TVFA and NH3-N values for caecum content of 12 weeks old NZW rabbits. ∆ It was observed that total bacteria count, total E. coli and lactobacillus counts were significantly affected due to feeding the diets containing 20 or 30% SBT (50 or 75 % replacement values of alfalfa hay) as compared to those of the control group. ∆ Feeding the SBT-diets significantly increased carcass yield and total edible parts but reduced the abdominal fat of rabbits.∆ It was observed that feeding the SBT-containing diets did not alter plasma concentrations of total protein, albumin, AST, ALT, triglycerides, total cholesterol, HDL-C or LDL-C of 12-week-old rabbits compared with the control group. ∆ Rabbits fed the prebiotic-supplemented diets displayed superior growth performance to that of the control group. ∆ Added dietary prebiotic had a positive effect on the digestibility coefficients of DM, OM, CP, EE, CF and NFE of growing rabbits. ∆ Added dietary prebiotic had a positive effect on caecal fermentative activities and caecal microbial activity of growing rabbits. ∆ The pH value, ammonia-N level, total bacteria count and lactobacills counts of rabbits fed the prebiotic-supplemented diets were significantly higher but E. coli count was reduced as compared to control ones. ∆ Dietary prebiotic supplementation caused positive effects on the percentages of carcass yield, total edible parts and abdominal fat weight of rabbits. ∆ Dietary SBT level by added prebiotic interactions were not significant for all criteria measured. CONCLUSION It is concluded that SBT can replace alfalfa hay up to 30 % in growing rabbits’ diets with better performance and carcass traits; prebiotic performs further improvements in rabbit growth, feed conversion and dressing-out percentage.