Garlic oil has a strong antibacterial activity against a wide range of gram-negative and gram-positive bacteria as well as, antifungal properties. This study aimed to assess the effects of spraying fertile hatching eggs of Japanese quail with garlic oil solution on embryonic development, hatchability, physiological parameters, post-hatch chick growth and bacterial load on eggshell surface. Four hundred hatching eggs of Japanese quails were equally divided into four treatment groups. Eggs of the first group served as a control group without any treatment. Also, eggs of the second group served as a control but sprayed only with distilled water. Eggs of the third and fourth groups were sprayed by 1ml/liter and 2ml/liter garlic oil solution, respectively. Embryo weight, shank length, body length as well as, chick weight, chick shank length, chick body length and hatchability tended to be higher significantly (P<0.05) in eggs treated with garlic oil solutions when compared with control eggs. While hatch time, embryonic mortality, egg albumen weight ratio, egg shell thickness and egg weight loss ratio at 14 days of incubation were significantly (P<0.05) decreased in eggs sprayed with garlic oil solutions when compared with control eggs. Blood hematological parameters (RBCs, Hb and PCV), plasma total protein, albumin, total lipids, hormones, immunoglobulin G (IgG) were significantly increased (p<0.05), while plasma glucose was decreased. There was no effects on plasma cholesterol compared to control. WBCs count was slightly increased in number in response to spraying with garlic oil solution. Carcass constituents of chicks at hatch and growth performance (body weight, feed intake and body weight gain) of chicks at 14 days of age recorded significant higher values and improved feed conversion in response to spraying with garlic oil solutions. In contrast, yolk residual of chicks at hatch was lower than control group. Application of garlic oil had significant influence on TBC on the surface of egg shell either at one week or after two weeks of incubation compared to control groups. Intestinal total aerobic, anaerobic micro-flora counts and the count of total coliform of chicks were decreased.
In conclusion, Spraying Japanese quail eggs with garlic oil solution as natural disinfectants (pre-incubation) is a good way to improve embryonic development, hatchability, blood constituents, hormones and immunity of hatching chicks and lowering the bacterial contamination of eggshell surface of quail eggs.