The responses to supplementing the diet of Single Comb White Leghorn (SCWL) cockerels with ethoxyquin were tested on two parameters: 1) tissue peroxidation and 2) immune response. In the first experiment, three concentrations of supplemental ethoxyquin (0, 500, and 1,000 ppm) were added to a basal diet and fed to SCWL cockerels for 6 wk. Tissue peroxidation was assessed by measuring the thiobarbituric acid reactive substances (TBARS) concentration in the liver, kidney, heart, and spleen. The TBARS concentration in response to 500 ppm dietary ethoxyquin was significantly lower in the liver and spleen tissues, whereas in the kidneys, 1,000 ppm ethoxyquin significantly lowered TBARS. In a second experiment, four concentrations of ethoxyquin (0, 125, 500, and 1,000 ppm) were added to a basal diet and fed to SCWL cockerels for 8 wk. The primary and secondary immune response were assessed by determining antibody titers to the Newcastle disease virus using hemagglutination inhibition (HI) and ELISA. The HI and ELISA titers for the primary and secondary immune response were not significantly different from the control. Analysis of body weight, feed conversion, and organ weight revealed no statistically significant differences between treatments, although in the second experiment the dietary treatment of 1,000 ppm ethoxyquin resulted in significantly higher relative liver weight.

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