الفهرس 
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Abstract
The present study was carried out at the Department of Animal Husbandry and Animal Wealth Development, Faculty of Veterinary Medicine, Alexandria University during the period extended from June 2020 to April 2021.
The experiment aimed to investigate the effects of different concentrations and delivery route of B. subtilis on Pre hatch performance, growth performance and immune response of Cobb500 broiler chickens.
Studied traits:
1. Embryonic mortalities and hatchability percentages including: early, mid
and late embryonic mortalities.
2. Weekly body weight was recorded from hatch to five weeks of age.
3. Relative growth rate.
4. Broiler carcass quality.
5. Histomorphological examination of jejunum and bursa.
6. Antibody titer against Newcastle disease virus vaccine, total leucocytic count, and lymphocytes transformation test.
The main findings were:
• There were non-significant differences were found for either hatchability percentages or hatchability of fertile eggs between injected and non-injected eggs. However, the control non-injected group) T1C) showed the higher non-significant hatchability (80%) followed by control negative) T1A) and non-injected treatment (T4) (both 79%) then those of injected with B. subtilis 1×1010 CFU/egg) T3) (77%). While, the hatchability of fertile eggs percentages was non significantly higher in
control negative) T1A) (86%) then non-injected treatment (T4) and control non inoculated eggs (T1C) (85.7% and 85%).
• The control negative group) (T1A) expressed the highest early embryonic mortality (7.0%) followed by the non-injected treatment (T4) (4.7%) and injected group with B. subtilis 1×107 CFU/eggs (T2) (3.0%). On other hand, the control non injected group) T1C (recorded the highest non-significant mid embryonic mortality (3.0%). Meanwhile, the injected treatment with B. subtilis 1×107 CFU/egg) (T2) exhibited the high non-significant late embryonic mortality (5.0%).
• The injected group with B. subtilis1×1010 CFU/egg (T3) showed the lowest significant hatch weight (46.98 gm) while there were no significant changes between other groups.
• The chicks injected with B. subtilis1×1010 CFU/egg (T3(reported the high significant sticky embryo percentage (9.0%) followed by those injected with B. subtilis 1×107 CFU/egg (T2) (6.0%) and control positive group T1B (5.7%) with no significant differences between them.
• Both treatments supplied with B. subtilis with 1×107 CFU either in ovo and in drinking water experienced the highly significant body weight at marketing age (5 weeks) (2218.72 and 2138.91).
• The treatment supplied with B. subtilis1×107 CFU/ml in drinking water (T4W1 (recorded the highly significant relative growth rate (RGR%) for all periods except for the last week. The RGR% of (T4W1) was 95, 66, 63.3 and 168.4% for overall RGR%. The treatment supplied with B. subtilis 1×1010 CFU/ml in drinking water (T4W2) showed the lowest significant overall RGR%.
• The relative weight of liver and trunk recorded the high significant value for group supplied with B. subtilis1×107 CFU/ml in drinking water (T4W1) as they recorded (2.6% for relative liver weight and 21.3% for relative trunk weight). While the group supplied with B. subtilis 1×1010CFU/ml in drinking water (T4W2) exhibited significant abdominal fat (1.3%). The in ovo supplied B. subtilis 1×1010 CFU (T3) showed the highest non-significant drumstick weight percentage (11.4%).
• The histomorphological examination of jejunum revealed that group which in ovo inoculated with B. subtilis1×107 CFU/egg (T2) showed the highly significant villus length (1279.25µm) followed by supplemented group in drinking water with 1×1010 CFU/ml (T4W2) then with 1×107 CFU/ml (T4W1) concentration (1206.36 and 1132.9µm). while the group supplemented with 1×1010 CFU/ml (T4W2) exhibited the highly significant villus width (122.45µm) followed by in ovo inoculated with 1×107 CFU/egg (T2) and 1×1010 CFU/egg (T3) (107.85 and 106.69µm respectively). The in ovo inoculated with 1×1010 CFU/egg (T3) had the lowest villus width and the highest crypt depth as well as the lowest ratio between villus height and crypt depth.
• The histomorphological examination of bursa showed that drinking water supplied with 1×107 CFU/ml (T4W1(experienced the highest significant bursal follicular length (814.33µm) followed by 1×1010 CFU/egg (T3) (797.95µm). While the bursal follicular area showed no significant differences between treatments except the group supplemented with 1×1010 CFU/ml (T4W2) exhibited the lowest significant area.
• The overall antibody titers showed that there were no significant differences between treatments except drinking water supplied with 1×107 CFU/ml (T4W1) had the highest non-significant antibody titer (23.67), while the findings of this study exhibited that supplementation of B. subtilis had no significant effect on antibody levels against NDV until the 3rd week, after immunization the first dose by 14 days. The highest significant levels of antibody titers were observed in in ovo inoculated with 1×107 CFU/egg (T2(, drinking water supplied with 1×107 CFU/ml (T4W1) and drinking water with 1×1010 CFU/ml (T4W2) (5.4, 5.2, 5.0; respectively).
• There were non-significant differences between treatments in overall lymphocytes transformation percentages, in ovo inoculated with 1×1010 CFU/egg (T3) had the highest lymphocytic transformation percentage at 2nd, 3rd, and 4th week of age (27.41, 27.23, 25.53%; respectively) however at 5th week drinking water supplied with 1×1010 CFU/ml (T4W2) was the highest (27.07%). While, the total leucocytic count showed significant increase in (T4W2) (15.20×103/mm3).