effect of different levels of terbutaline on performance, carcass traits and blood metabolites in boiler chicks

an experiment was conducted under completely randomized design to investigate effect of various levels of terbutalin, a bete-adrenergic agonist, by procuring 120, 35-d age male cobb broiler chicks from d 29-49. the birds were randomely distributed into 3 treatments and 4 replicates with10 birds each. the birds were fed experimental diets with different levels of terbutaline at levels 0.0 (control), 7.5 and 15 ppm/kg. feed intake and liveweight were weekly measured. at the end of the experimental periods, 20 chicks from each group were randomly selected and blood samples were collected, 8 birds also were selected for carcass analysis. blood metabolites were assayed via spectrophotometric methods and hormones via radioimmunoassay. results showed that terbutaline at lower level of inclusion had significantly affect on weight gain, feed intake and feed conversion ratio vs. control group (p<0.05). low level of terbutaline caused significant increases in carcass weight, carcass yeild, breast weight and thigh weight as 10.3, 5.2, 3.4, 4.8% and decreased in abdominal fat as 22.8% as compared to control group, respectively (p<0.05). terbutaline inclusions significantly increased protein percentage of breast and thigh and decreased fat percentage of breast vs. control (p<0.05). both levels of terbutaline inclusion had significantly increased in blood glucose, triglycerides, cholesterol and thyroxine levels, but decreased in blood insulin, urea nitrogen and uric acid levels (p<0.05). it has no significant effects on blood alanine, glutamine, creatine kinase and aspartate amino-transferase enzymes levels. in general, the results showed that terbutaline inclusions especially in 7.5 ppm/kg in broiler diets can improve performance and carcass traits.