EFFECT OF HIGH LEVELS OF ZINC ON PLASMA METALLOENZYMES ACTIVITY AND BLOOD PARAMETERS IN BROILER CHICKS

Alkaline phosphatase is a metalloenzyme containing approximately 0.15 % of zinc. One hundred and forty-four one-day-old Ross 308 broiler chicks were used in the experiment. Three zinc levels (40, 120 and 200 mg/kg) were added to the basal diet to establish the treatments. On d 21 and 42 average body weight gain (BWG), average daily feed intake (ADFI) and feed conversion ratio (FCR) were obtained by pen. At 42 d heterophil/lymphocyte ratio (H/L), an indicator of stress in birds, were counted and also plasma was used for measurement of plasma minerals concentration (Ca, P, and Cu), cholesterol, and serum enzyme activity of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) by an automated chemistry analyzer. No dietary treatment significantly altered ADFI, BWG and FCR at days 21 and 42. Both 120 and 200 mg Zn/kg diet resulted in a significant reduce in H/L ratio (p 0.05). Adding additional Zn resulted in significant decrease of blood P, Cu and cholesterol concentration (p 0.05). Supplementation the diet of broiler chicks with additional levels of zinc resulted in significant (p 0.05) increase in blood plasma ALP and LDH. The overall results of this study show that levels of 120 and 200 mg Zn/kg diet could be effective in decrease of H/L ratio and cholesterol and increase of ALP and LDH without any harmful effect on performance traits.