Effects of different antibiotics on performance, processing characteristics, and parts yield of broiler chickens.

Broilers were grown to 49 days of age on diets supplemented with bambermycins (BAM, 2.2 ppm), bacitracin methylene disalicylate (BMD, 27.5 ppm), virginiamycin (VM, 11 ppm), or an unmedicated control. Samples of birds were processed for dressing percentage and parts yield. There were no significant (P greater than .05) effects of antibiotics on final body weight, feed conversion, or mortality. In male broilers, BMD and VM significantly (P less than or equal to .05) increased dressing percentage and percentage yield and reduced the skeletal rack as a percentage of postchill weight compared to those fed the nonmedicated control. All antibiotics significantly increased breast skin weight and breast skin as a percentage of postchill weight of as compared with those fed the unmedicated control. In female broilers, BAM and BMD significantly increased dressing percentage and percentage yield and increased breast weight and breast as percentage of postchill weight as compared with those fed the unmedicated control diet. Females fed BMD also had significantly heavier leg quarters and breast skin than those fed the unmediated control. Females fed VM had increased breast skin weight and breast skin as a percentage of postchill weight than those fed the unmedicated control. The results of the present study indicate that antibiotics may influence dressing percentage and parts yield in the absence of improvements in body weight gain or feed utilization.