The experiment was conducted at the Faculty of Agriculture University of Ain Shams-Egypt, from January to March 2008, to study the effect of different levels of chromium yeast (Cr-yeast) on broiler chickens performance, carcass quality and enzyme activity through 35 days of experimental periods. A total of 450 one-day old unsexed chickens (Cobb) strain were used. The birds were randomly allocated to five treatments with 3 replicates each. The treatments were control (T1) without supplementation and T2, T3, T4 and T5 which were supplemented with 0.5, 1, 1.5 and 2 mg Cr-yeast /kg diet, respectively. Live body weight and weight gain were significantly (p<0.05) higher when Cr-yeast were supplemented at 1 (T3), 1.5 (T4) and 2 (T5) mg/kg diet. Feed conversion was significantly (p<0.05) better when Cr-yeast was supplemented at levels of 1 (T3) or 1.5 (T4) mg/kg diet. Dressing percentage, percent cuts were not affected by dietary supplementation of Cr-yeast. Amylase level in both jejunum and ileum increased significantly (p<0.05) in the groups supplemented with 1 (T3) or 1.5 (T4) mg Cr-yeast, while other enzyme levels were not significantly different among control and supplemented groups. However, enzyme levels of supplemented groups were numerically higher than the control. Protein percentage in the breast and thigh increased significantly (p<0.05) in all Cr-yeast supplemented groups as compared to the control group, while fat percentage in the breast and thigh decreased significantly (p<0.05) when Cr-yeast level increased from 1-2 mg/kg diet. It can be concluded that Cr-yeast had a beneficial effect on some of the productive measurements of broilers under such experimental conditions.
