A total of 546 fertile eggs were divided randomly to 7 treatments in three replicates, 26 eggs in each, as follows: The 1^st treatment served as a control (without injection), the 2^nd, 3^rd and 4^th treatments were injected with 0.1 ml deionized water containing 25, 50 and 75 μg/egg zinc sulfate, respectively and treatments 5^th, 6^th and 7^th injected with 0.1 ml deionized water containing 25, 50 and 75 μg/egg ZnO-NPs, respectively. Eggs injection was performed at the 9^th day of incubation. 
The results could be summarized as follow:
The treatments did not cause any significant differences in the hatchability %, embryonic mortality, chick weight, chick weigh %, the relative weight  of residual yolk sac, heart, liver,gizzard and proventriculus to body weight (BW) or yolk free body weight of chicks at one day of age, slaughter parameters ( percent of carcass, breast, thighs, abdominal fat, liver, heart and gizzard) at 35 days of age or hematological parameters and plasma constituents at one and 35 days of age compared to the control. 
Significant differences were found in body weight (BW) at 21 and 35 days of age, and the highest value was recorded of the group 75 µg/egg zinc sulfate followed by 25 µg/egg  ZnO-NPs in ovo injection. It is concluded that using of 75 μg/egg zinc sulfate or 25 μg/egg  ZnO-NPs in ovo injection at 9 days of incubation, could be recommended  to ,  enhance the growth performance  traits without harmful effects on the physiological responses.