Abstract
Four hundred non sexed one-day old Japanese quail chicks were randomly allotted into four experimental groups (100 chicks/group). The first group (control) fed on the basal diet without any supplement while, the second to fourth groups fed on the basal diet supplemented by 0.25, 0.5 or 0.75 g of essential oils and organic acids blend (Biacid) respectively. During the experimental period (6 weeks) it was observed that using essential oils and volatile fatty acids (VFAs) blend at 0.25 or 0.5g/kg in the diet increased final quail chicks weight by about 4.1% and 9.9% respectively when compared with the control, while higher level (0.75g/kg diet) had no effect on quail chicks body weight. Also, there was a significantly increased body gain by about 4.3% and 10.6% respectively when compared with the control, while higher supplementation level had no significant effect on quail chicks weight gain. It was found that using a blend of essential oils and VFAs decreased the total feed intake of quail chicks and non-significantly improved feed conversion and protein efficiency ratio when compared with the control. On the other hand, it was observed that using essential oils and volatile fatty acids blend especially at 0.5g/kg diet increased neutrophil percentage, phagocytic activity and antibody production against Newcastle disease vaccine (NCDV) and had no adverse effect on kidney or hepatic cells function when compared with the control. Moreover, the use of Biaicd in Japanese quail chicks ration reduced total bacterial counts and E.coli in the cecal content, while increased Lactobacillus counts in the cecal content when compared with the control one.

Key words: Essential oils - Organic acids - Growth performance – Immune response – Intestinal microbiology - Quail chicks.