Physiological responses of broiler chicks fed various level of dopamine and zinc

The influences of dopamine (DA) and zinc (Zn) on some physiological parameters of plasma such as growth hormone, cholesterol, 3-glyceride and growth rate, feed conversion ratio and abdominal fat of broilers between the ages of 21 to 42 day were investigated. The experiment was designed on a total of 180 commercial meat-type chicks as a randomized complete block with a 3x2x2 factorial arrangement of treatments with three levels of DA (0, 50 and 100 mg kg(-1)) and two levels of Zn (0 and 40 mg kg(-1)) in each sex. At the first day of trial, chicks were randomly distributed in 36 boxes at the same condition until day 15. Then, the treatments were administered in a low dosage for acclimating of chicks to them. From day of 21, the main dose of treatments was used. The effects of DA and Zn and interaction between them on cholesterol concentration of plasma were significant (p < 0.05). But the effects on concentration of growth hormone (GH) and 3-glyceride of plasma were not significant. The maximum concentration ofcholesterol in plasma was observed in male chicks administered 40 mg kg(-1) of Zn and the minimum concentration was related to female chicks administered 50 mg kg(-1) of DA. In this period, the main and interaction effects of all treatments on weight gain mean of chicks were significant. Also, Zn and DA and interaction of DA x sex improved feed conversion ratio (p < 0.05). The results of this experiment confirmed the lipolytic effect of DA on plasma cholesterol and abdominal fat and also showed that consumption of 100 mg kg(-1) of DA plus 40 mg kg(-1) of Zn cause to improve growth performance of male chicks.