الفهرس 
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Abstract
The present experimental studies were conducted at the laboratories of the Department of Environmental Biotechnology, Genetic Engineering and Biotechnology Research Institute and Livestock and Fisheries Research Development, Arid Lands Cultivation and Development Institute, City of Scientific Research and Technology Applications and at the Poultry Research Farm belonging to Animal and Fish Production Department, Faculty of Agriculture (Saba Basha), Alexandria University, during the period from May 2008 up to October 2010.
The primary objectives of these studies were to isolate, identify and characterize local spore-forming bacteria (Bacillus subtilis) from wetted rice straw in Egypt, for potential application as a probiotic feed supplement for chickens. Also, to study the effect of identified bacteria (Bacillus subtilis-isolate BS14) which used into two different routes as probiotic supplements broilers in feed and/or drinking water on performance of broiler chickens, nutrients digestibility, carcass quality, and blood plasma constituents, haematological indices and differential leukocyte counts, antibody titers against Newcastle disease virus (ND), histological alterations of intestinal villi in chickens and also, their effects on economical benefit from one week to 6 weeks of age in a completely randomized experimental design.
The experiments divided into several parts:
I. Collection, isolation, identification and Screening of Bacillus subtilis-isolate BS14 for
probiotic properties
II. Evaluation of Bacillus subtilis-isolate BS14 activity as dietary probiotic for broiler chicks.
III. Influence of Bacillus subtilis-isolate BS14 on immune-response of broiler chickens
V. Histopathology studies (Morphometric Analysis).
Two hundred and forty unsexed, one day old Cobb broiler chicks were distributed randomly into 6 treatment groups. Each group contained 40 birds, replicated 4 times. Chicks in all experimental groups were fed a basal starter diet from 1 to 21 days of age and a basal grower diet from 22 to 42 days of age. The basal diets were un-supplemented or supplemented with the following:
1. Basal diet only without supplementation (served as negative control).
2. Basal diet + 1 % commercial probiotic Super Bio-Buds (used according to the manufacturer instructions and used as positive control)
3. Basal diet + 1 % locally prepared probiotic (1x1012cfu of Bacillus subtilis-isolate BS14)
4. Basal diet + 1 % locally prepared probiotic (1x1010cfu of Bacillus subtilis-isolate BS14)
5. Basal diet + 1 % locally prepared probiotic (1x1011cfu of Bacillus subtilis-isolate BS14) adding on drinking water at 1st, 7th, 14th and 21st days.
6. Basal diet + 1 % locally prepared probiotic (1x109cfu of Bacillus subtilis-isolate BS14) adding on drinking water at 1st, 7th, 14th and 21st days.
The main obtained results could be summarized as follows:
I. Iidentification and Screening of Bacillus subtilis-isolate BS14 for probiotic properties
1. The results of identification based on Morphology and (PCR-RFLP) analysis of the 23S rDNA presented that isolates 4 and 7 are very close each to other and to the Bacillus subtilis reference strain ATCC 6633. Based on identification results, Bacillus subtilis-isolate BS14 (isolate 4) was selected for the following experiments.
2. The maximum growth was obtained when the Bacillus subtilis-isolate BS14 was grown on either glucose (60 mg/ml) or sucrose (7.5 mg/ml) respectively, while the lowest CDW was recorded with xylose 0.6 mg/ml. The highest carbohydrate value in (CFS) was recorded with mannose (12.35 mg/ml) and sucrose (5.8 mg/ml) while the lowest carbohydrate value was obtained with maltose (0.12 mg/ml). The highest lipid yield was recorded with sucrose 0.259 mg/ml and maltose (0.251 mg/ml) respectively. Glucose is the preferred carbon and energy source of B. subtilis.
3. The maximum enzyme activity (7.03 U/ml) was attained with glucose, 89 cfu/ml exhibiting and 1.44 mg protein/ml. The highest CFU value (200 cfu/ml) was counted with sucrose; however its enzyme activity was as low as 1.24 U/ml exhibiting the lowest of both specific activity (0.77U/mg protein) and specific productivity (1.65 U/g cells).
4. The production of both lactic and acetic acids was particularly similar with all tested carbon sources. Quantitative determination of organic acids is important for monitoring bacterial growth and activity and for nutritional reasons.