The aim of this study was to determined the toxic effects and biochemical changes induced by amitraz in the chicks (7-14 days). The median lethal dose (LD50) of amitraz was (53.05 mg / kg, orally. Yohimbin injection at (0.5, 1 mg / kg, intraperitoneally) 10 minutes befor the oral administration of amitraz increased the LD50 of amitraz to (64.27 and 74.44 mg / kg, orally), respectively. The signs of amitraz toxicosis are closing eyelid, ruffled feather, dropping of the wings, watery feces,

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... tion, recumbency on the sternum and death were reduced in intensity by yohimbin injections. Tow hours after the oral dosing amitraz at (20 and 40 mg / kg orally) significantly increased plasma glucose concentration in the chicks (280.40±7.62 and 293.68 ± 9.23mg / dl) in comparison with the control value (226±6.75 mg / dl) and significantly increased plasma cortisol level (10.85 ± 4.98 and 12.27 ± 1.63 ng/ml) in comparison with the control value (9.12 ± 2.2 ng/ml). Amitraz at (40 mg/ kg, orally) significantly increased plasma ALT, AST, ALP and CPK activities when compared with control values. The results suggest that amitraz is highly toxic in chicks in comparison with other laboratory animals and mammals which adversely affects the liver, heart and the bone and caused stressful condition in the birds.