The effect of in ovo or day-of-hatch subcutaneous antibiotic administration on competitive exclusion culture (PREEMPT (TM)) establishment in neonatalchickens

The effect of in ovo or day-of-hatch subcutaneous antibiotic administration on the detection of antibiotic residues in yolk sac or blood serum samples and the potential for observed residues to interfere with competitive excl usion (CE) culture establishment was compared in three experiments. The in ovo or subcutaneous administration of gentamicin sulfate or ceftiofur sodiu m was associated with detectable levels of antibiotic residues in yolk sac or blood serum samples in Experiment 1. Further, the ability to detect anti biotic residues in day-of-hatch chicks was associated with reduced levels o f CE culture establishment when cecal propionate level, an indicator of PRE EMPT(TM) establishment, was determined following PREEMPT(TM) application by oral gavage on the day of hatch in Experiments 1 and 2. Restricting chicks from feed, as opposed to providing access ad libitum to a starter ration, for 6 h immediately following administration of PREEMPT(TM) improved (P < 0 .05) CE culture establishment in Experiment 2 in nonantibiotic injected con trol chicks, but did not affect (P > 0.05) experimental groups receiving ei ther gentamicin sulfate or ceftiofur sodium by either in ovo or subcutaneou s routes. The in ovo administration of 0.1 or 0.2 mg ceftiofur sodium to in dividual embryos on Day 18 of embryogenesis in Experiment 3 was associated with marked depressions (P < 0.05) in cecal propionate levels compared with uninjected control chicks. When feed was restricted and the time of PREEMP T(TM) administration was delayed for 48 or 72 h posthatch, mean cecal propi onate levels in in ovo ceftiofur sodium-injected chicks were not significan tly different (P > 0.05) from controls, indicating a time- and feed restric tion-associated effect on improving CE culture establishment.