A total of 450 fertile Japanese quail eggs were used to determine the impacts of in ovo administration of water-soluble vitamins (C, B6 and B12) on the growth performance, carcass traits, hematological and biochemical blood parameters as well as the immune response of Japanese quails. On the 7th day of incubation, the eggs were allocated to five groups: un-injected, 0.1 ml/egg saline, 1 mg/egg vitamin C, 150 µg/egg vitamin B6 and 20 µg/egg vitamin B12. The percentage of early embryonic mortality was increased (P≤0.001) in all treated groups versus the control group. Chicks that hatched from eggs injected with 1 mg/egg vitamin C exhibited a significantly greater (P≤0.05) live body weight (LBW) than those from the control and saline groups. During 0–2 weeks of age, the chicks hatched from eggs injected with vitamins displayed better feed conversion than the positive or negative controls. In ovo injection of vitamins had no significant effect on all carcass traits. In ovo injection with vitamins C, B6 and B12 increased plasma total protein and its fractions compared with the control. Plasma levels of total lipids and cholesterol were decreased in chicks hatched from eggs injected with 1 mg/egg vitamin C, 150 µg/egg vitamin B6 or 20 µg/egg vitamin B12 compared with those hatched from control eggs. Plasma T3 and T4 were increased in chicks hatched from eggs injected with vitamin C, vitamin B6 and vitamin B12. The relative weights of the bursa of Fabricius and thymus were significantly (P=0.002 or 0.003) increased in the birds hatched from eggs injected with vitamins compared with those in the control or saline group. Thus, in ovo injection of vitamins C, B6 and B12 improved the blood profile and immune response of Japanese quail.
