This study was conducted to investigate the effects of fennel ethanol extract on egg production, serum parameters, and bone attributes of laying hens administered carbon tetrachloride (CCl4). A total of 192 Hy-Line W-36 laying hens were assigned to four treatments of four replications in a completely randomized design for 9 weeks (36-44 weeks of age). Experimental groups consisted of 1) positive control (PC) diet (basal diet only), 2), negative control (NC) diet (basal diet + 30 mL CCl4/kg diet), 3) NC diet plus 50 mg fennel extract/kg diet (50F), 4) NC diet plus 100 mg fennel extract/kg diet (100F). Egg production and feed intake were recorded weekly. At the end of the experiment, blood samples were collected and bone mineralization and strength were measured. The higher dose of fennel extract (100 mg) increased (P < 0.05) egg production and feed intake, and decreased (P < 0.05) cracked egg percentage compared to positive control group. Serum concentrations of Ca and P were also higher in this group (P < 0.05) while the lipid levels and activities of hepatic enzymes in the serum were lower (P < 0.05). This group also had improved (P < 0.05) Ca and P retention in tibia bone, and also greater tibia shear force and stiffness. However, these improvements did not restore the state to the same level as that observed in chickens in the positive control. In conclusion, supplementing 100 mg of fennel extract to diets of layers administered with CCl4 partially ameliorates the detrimental effects of CCl4, and also could improve egg production, serum parameters, and bone attributes.

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