Histology of the Growth Plates of the Leg Bones in Ostrich (struthio Camelus) with Tibiotarsal Rotation

s of papers 29 collected daily and subjected to bioassay for detectable antimicrobial residues in yolk. Antimicrobial residues were not detected during the 7 days of treatment or the subsequent 3 days following cessation of treatment in the control, sulfadimethoxine or tylosin treatment groups. However, detectable residues were observed in eggs derived from enrofloxacintreated hens on days 6,7,9 and 10 of the study. In experiment 2, antimicrobial residues were only detected in yolks from hens treated with enrofloxacin. A subset of eggs from each group were collected at days 3-6 or 13-15 and were incubated and treated with PreemptTM at hatch. When 48 hr cecal propionate concentrations were used as an index of culture establishment, reduced (P<.05) efficacy was observed only in chicks derived from enrofloxacin-treated hens at either collection period. While several antibiotics do not appear to produce detectable egg residues or interfere with CE establishment, these data suggest that chicks derived from enrofloxacin-treated hens may not be candidates for safe and effective CE culture treatment.