The current study was designed to probe pathological effects of colistin in growing broilers. One hundred twenty day-old broiler chicks were divided into six equal groups A-F. These birds were injected colistin sulphate, 0, 5, 10, 20, 40 and 80 mg/kg BW respectively through intramuscular route. The different serum-biochemical parameters including total protein, albumen, globulin, ALT, AST, LDH, GGT, creatinine and BUN were determined at day 21 and 42 of experiment. The hematological parameters including RBC, WBC, PCV and Hb were determined twice. The serum total protein values were significantly higher in group E as compared with control group. At day 42 groups, C-E had significantly lower albumen values as compared to group A. The similar pattern was observed in globulin values. The creatinine & urea was also found significantly higher in group D and E at day 21 of experiment, while at day 42 all the groups having significantly higher urea level in comparison with group A indicating nephrotoxic effect of colistin. The serum enzymes including ALT and AST were significantly higher in group D & E as compared with group A, which is an indication of liver damage. The LDH and GGT values showed significantly increasing trend in experimental groups compared with control. The erythrocytes and leucocytes count were significantly higher in control and low dose groups as compared with higher colistin dose groups. It is concluded that lavish parenteral administration of colistin resulted in increased levels of hepato-renal serum indicators and lower values of hematological parameters.

Key words: Broilers, Colistin, Hematology, Kidneys, Liver, Serum biochemistry