Effect of antibiotics on tissue trace mineral concentration and intestinal tract weight of broiler chicks.

Two experiments were conducted with broiler-type chicks to determine the effect of antibiotics on intestinal weight and kidney, bone, and liver trace mineral concentrations. All antibiotics were in diets at the manufacturers' recommendations. Feed intake of experimental diets (antibiotics or non-treated control) was restricted to 90% of that of an additional group fed the control diet ad libitum. Feed intake, weight gain, and feed efficiency were not affected (P greater than .10) by dietary treatments. Virginiamycin decreased intestinal weight an average of 19% as compared with 14% for bambermycins and oxytetracycline, 6% for Zn bacitracin, and 18% for lincomycin. Except for Zn bacitracin, all antibiotics produced intestinal weights which were lower (P less than .01) than those of controls. Only virginiamycin increased (P less than .01) kidney Mn concentration. Bone Mn concentration was greater (P less than .01) for virginiamycin than bambermycins or oxytetracycline in Experiment 2, and greater (P less than .05) for lincomycin than virginiamycin or Zn bacitracin in Experiment 2. Feeding Zn bacitracin increased (P less than .01) bone Zn concentration whereas feeding virginiamycin caused a decline (P less than .05) in bone Zn concentration in Experiment 1. There were no differences in Cu, Zn, or Fe concentrations in liver or kidney.