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

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 exclusion (CE) culture establishment was compared in three experiments. The in ovo or subcutaneous administration of gentamicin sulfate or ceftiofur sodium was associated with detectable levels of antibiotic residues in yolk sac or blood serum samples in Experiment 1. Further, the ability to detect antibiotic residues in day-of-hatch chicks was associated with reduced levels of CE culture establishment when cecal propionate level, an indicator of PREEMPT establishment, was determined following PREEMPT 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 improved (P < 0.05) CE culture establishment in Experiment 2 in nonantibiotic injected control chicks, but did not affect (P > 0.05) experimental groups receiving either gentamicin sulfate or ceftiofur sodium by either in ovo or subcutaneous routes. The in ovo administration of 0.1 or 0.2 mg ceftiofur sodium to individual 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 PREEMPT administration was delayed for 48 or 72 h posthatch, mean cecal propionate levels in in ovo ceftiofur sodium-injected chicks were not significantly different (P > 0.05) from controls, indicating a time- and feed restriction-associated effect on improving CE culture establishment.

Effect of lactose administration in drinking water prior to and during feed withdrawal on Salmonella recovery from broiler crops and ceca.

Salmonella contamination of the chicken crop has been reported to increase markedly and significantly during feed withdrawal, probably due to coprophagy, and may contribute to carcass contamination at processing. The effect of prolonged lactose administration (2.5%) in the drinking water on the incidence of Salmonella recovery from broiler crops or ceca was evaluated in seven experiments. In these experiments, all or a percentage (providing seeders and contacts) of 7-wk-old broilers were challenged with approximately 1 x 108 cfu Salmonella enteritidis and provided lactose for 5 or 11 d prior to and during an 18 or 24 h feed withdrawal period. A small but significant lactose-mediated reduction in Salmonella contamination of crops was observed in one of two identical experiments with 18 h feed withdrawal. Extending the feed withdrawal period to 24 h did not improve the ability of lactose to affect Salmonella recovery from crops or ceca. Similarly, lactose did not affect Salmonella recovery when the percentage of birds challenged was reduced to 3 out of 16 and Salmonella recovery from crops or ceca of unchallenged, contact broilers was measured. Extending the duration of exposure to 2.5% lactose in the drinking water from 5 to 11 d did not improve the ability of lactose to affect Salmonella recovery. Taken together, these data suggest that provision of 2.5% lactose in the drinking water during the last 5 to 11 d of growout prior to slaughter will not be useful in an integrated Salmonella control program under commercial conditions.

Evaluation of potential disinfectants for preslaughter broiler crop decontamination.

The broiler crop has recently been implicated as a major source of Salmonella contamination at commercial processing. Furthermore, feed withdrawal has been positively correlated with increased Salmonella incidence in the crop, probably due to coprophagy. In the present study, a rapid screening assay was developed to evaluate several potential disinfectants in the presence of large quantities of organic matter, simulating the crop environment. An apparent synergistic combination of d-Limonene (DL) and citric acid (CA) was observed when evaluating the potential to eliminate Salmonella in the presence of organic material. A method of encapsulation of DL and CA was developed for voluntary consumption by broilers during feed withdrawal. During an 8-h feed withdrawal individual 8-wk-old broilers voluntarily consumed an average of 21.5 capsules (total of 3.44 g material). When eight capsules were force-administered to Salmonella-challenged 8-wk-old broilers during an abbreviated 4 h feed withdrawal, Salmonella was not recovered using selective enrichment. To evaluate the effect of voluntary capsule consumption, 8-wk-old broilers were challenged with 1 x 108 cfu of Salmonella 5 d prior to an 8 h feed withdrawal. When these broilers were allowed unlimited continuous access to capsules containing DL/CA during an 8 h feed withdrawal, 24.8 capsules per broiler were ingested without affecting Salmonella recovery from crops. When access to capsules containing DL/CA was limited to the final 45 min of an 8 h feed withdrawal in a similar experiment, an average of 22.2 capsules were consumed by each broiler, resulting in a significant decrease in the number of Salmonella-positive crops. Although a number of practical questions and considerations remain, these data suggest that appropriate disinfectants could be administered during preslaughter feed withdrawal for the purpose of reducing foodborne pathogens in crops.

Comparison of enrichment methods for recovery and chick infectivity of chlorine-injured Salmonella enteritidis.

In recent years, several preenrichment media have been shown to be effective for use in the recovery of sublethally injured Salmonella organisms. Selective enrichment without preenrichment has resulted in a lower recovery of organisms, particularly with regard to injured or stressed salmonellae. The present experiments compared the ability of nonselective preenrichment followed by selective enrichment or direct selective enrichment alone to recover chlorine-injured Salmonella organisms. Additionally, the Salmonella detection limits of the two enrichment methods were compared with minimal infectious dose in neonatal chicks. In three experiments, Salmonella enteritidis cells were exposed to chlorine for specific times and subsequently cultured by using preenrichment followed by selective enrichment or selective enrichment alone. Simultaneously, neonatal chicks were orally challenged with S. enteritidis cells from each exposure time to chlorine. The results indicated a marginal, but significantly (P < 0.05) higher level of recovery of sublethally injured salmonellae by using nonselective preenrichment followed by selective enrichment, as compared to selective enrichment alone. Interestingly, both culture methods were capable of detecting injured S. enteritidis cells at levels incapable of infecting neonatal chicks.

Evaluation of alternative sampling methods for Salmonella critical control point determination at broiler processing.

Several sampling methods have been developed for the detection of Salmonella on broiler carcasses during commercial processing. The present study evaluated three sampling methodologies for sensitivity of Salmonella detection on processed broiler carcasses. Furthermore, the effect of crop removal or chill tank exposure on the frequency of Salmonella recovery was also examined. In two experiments, swab, skin, and carcass rinse samples were compared for sensitivity of Salmonella detection. The results indicated that culture of swabs was less effective (P < 0.05) for Salmonella detection than either skin or carcass rinse samples. No significant (P > 0.05) differences were observed in Salmonella recovery from culture of skin or carcass rinse. In two subsequent experiments, skin and carcass rinse samples were found to be equally sensitive in their ability to detect Salmonella. Additionally, the stages of processing between feather and crop removal were observed to cause significant (P < 0.05) increases in Salmonella recovery within an individual flock. Similar increases (P < 0.05) in Salmonella recovery were also observed following crop removal and immediately following immersion chilling in two separate flocks. These results suggest that culture of skin samples obtained from the thoracic inlet region may be a viable alternative to the traditional whole carcass rinse method for sensitivity of Salmonella detection. Furthermore, these experiments provided some evidence that the majority of Salmonella cross-contamination of carcasses prior to immersion chilling occurred following evisceration, with the chill tank potentially providing a major site for cross-contamination between Salmonella-negative and-positive flocks.