Effects of higher levels of chromium and copper on broiler health and performance during the peak tropical summer season

The effects of higher levels of chromium alone, and in combination with copper, were investigated in broiler chicks divided into seven equal groups. Group G served as control, receiving no treatment. Groups A, B and F received chromium chloride at a rate of 2 g/kg and nicotinic acid 150 mg/kg, while groups C, D and E received chromium chloride 8 mg/kg and nicotinic acid 150 mg/kg. Broilers in groups A and C received copper sulfate at a rate of 200 mg/kg, while groups B and D received 400 mg/kg feed. Both live and carcass mass showed non-significant difference between treatment groups and control during the treatment period. However, during the withdrawal period these were higher (P<0.05) in chromium-fed birds (alone and in combination). Feed conversion ratio (FCR) was better in the treatment groups. Relative mass of liver to body mass during the first two weeks showed lower (P<0.05) values in birds fed low levels of chromium alone, or in combination with two levels of copper, and those fed high levels of both compounds, compared with control. At the third week the relative mass of liver to body mass was high in all treatment groups than in the control. Relative mass of lung to body mass showed a significant increase in birds fed higher levels of both chromium and copper during the early period, whereas it decreased significantly after the third week than in the control group. During the withdrawal period, relative mass of kidney, lung and heart to body mass were lower (P<0.05) in birds fed chromium alone. Relative heart mass to body mass during termination of treatment showed a significant relationship with relative liver (0.99, P<0.05) and lung (0.99, P<0.05) mass to body mass in the low chromiumfed group, while during the withdrawal period a significant relationship developed of relative heart mass with relative liver (0.99, P<0.05) and lung (0.78, P<0.05) mass to body mass in birds fed high chromium with high copper. Both gross and histological studies showed no change in any organ studied.