Abstract
Two hundred day old chicks were used and allotted into equal five groups fed on the basal diet supplemented by 0.0, 25, 50, 75 and 100 mg allicin/Kg diet respectively for five continuous weeks. Dietary allicin supplementation at 25, 50 and 75mg/kg diet significantly (P≤0.05) improved final body weight and total gain by about (6.87%, 12.76% and, 10.13%) and (6.9%, 13.03% and 10.3%) respectively when compared with control broiler chick group. In contrast high level (100mg/Kg) addition of allicin non significantly (P≥0.05) decreased final body weight and total gain of broiler chicks by about 1.13 % and 1.2% respectively, when compared with control one. Allicin supplementation increased feed intake of broiler chicken while, 25, 50 or 75 mg allicin/Kg diet improved feed conversion ratio, protein efficiency ratio, efficiency of energy utilization and performance index when compared with control. In contrast high inclusion rate of allicin deteriorate the mentioned parameters. Allicin supplementation at different levels in broiler chicken ration had no significant effect on WBCs counts, and increased RBCs, Hb%, PCV%, blood serum units and reduced blood serum triglycerides and total cholesterol concentrations when compared with the control. On the other hand, allicin supplementation at 25, 50 or 75 mg/Kg diet improve kidney and liver functions through reduction of blood serum creatnine, GOT, GPT and ALP concentrations when compared with the control, while higher level showed adverse effect. Moreover, it was observed that allicin supplementation improved broiler chicken immune response through increased nutrophil percentage and weight of immune organs when compared with the control one. Dietary allicin supplementation at 25, 50 or 75 mg/Kg diet improved organic matter, crude protein and ether extract digestion, while high inclusion level exhibited lower digestibility percentage and numerically improved dressing percentage of broiler chicken, while had no effect on liver, gizzard, heart weight when compared with the control. Allicin supplementation at 50 mg/Kg diet improved economic efficiency of broiler chick's production.

Key words: Garlic extract, allicin, growth performance, immune response, nutrient digestibility, broiler.