Abstract
The aim of the present study was to determine the best method as well as appropriate concentration of Bacillus subtilis (B.subtilis)that can be applied to maximize the hatching and growth performances of broiler chickens. A total of 480 Cobb500 broilers fertile hatching eggs were assigned to five experimental groups (T1, T2, T3, T4andT5) as follows: T1assigned to three subgroups; One: it Penetrated and sealed without injection (control negative); Two: Eggs injected with 0.1 ml of physiological saline 0.9 NaCl (control positive) and the third: contains eggs that didn’t receive any pre-hatch treatment.T2 and T3 are the groups injected by B.subtilis while T4 and T5 are the eggs that didn’t receive any pre-hatch treatment. On the 18thday of incubation, 100 μL of 107 and 1010 CFU of B. subtilis/egg or saline was injected into the air cell of T2, T3 and the control positive eggs; respectively. Hatched chicks were re- assigned according to way and concentration of B. subtilis application toT1,T2,T3,T4 and T5groups; control group with no probiotic treatment ,inovo inoculated by 107 CFU/egg, 1010 CFU/egg, water supplementation by107 CFU/ml and 107 CFU/ml then managed for 35 days. Results revealed that, neither in ovo inoculation nor watery administration of B.subtilis of different concentrations had significant effect on hatchability parameters of incubated broiler eggs except increment of sticky embryo percentages in all treated groups. Broilers that supplemented in ovo via 107B.subtilis/egg had better weekly body weight, highest RGR% and the lowest FCR through the experimental period. Irrespective of the method of B. subtilis supplementation to broiler,107concentration of B.subtilis showed the highest significant marketing weight (p<0.001). It was concluded that in ovo inoculation didn't affect hatching performance but had beneficial improvement in growth performance of broilers.

Key words: Bacillus subtilis, Broilers, growth performance, hatchability, inovo, water supplementation.