The use of an antimicrobial and competitive exclusion combination in Salmonella-infected pullet flocks

Elimination of early Salmonella enteritidis infection after treatment with competitive-exclusion culture and enrofloxacin in experimentally infected chicks

The effect of normal avian gut flora (NAGF) and enrofloxacin administration on the early infection of young chicks by Salmonella enteritidis (SE) was determined using day-old White Leghorn chicks. Day- old chicks were divided into two groups, untreated control and NAGF-treated, and then infected with 10(6) cfu of SE per chick by oral gavage. The untreated, infected chicks were further divided into two groups and were either left untreated or medicated with a regimen of 10 mg/kg of enrofloxacin in drinking water daily for 10 d, followed by two doses of NAGF beginning at 10 and 8 wk of age in Trial 1 and Trial 2, respectively. Liver, spleen, and cecum samples were tested for the presence of SE, and immunological responsiveness was investigated up to 12 wk of age. Compared with the untreated group, the cecal colonization of SE was significantly (P < 0.05) decreased in the NAGF-treated group in Trials 1 and 2. No significant differences in organ infection were observed in the NAGF-treated vs. untreated birds. Although a significant effect of the combined treatment of enrofloxacin treatment and NAGF on the early infection was not shown in Trial 1, compared with enrofloxacin only or the untreated group, a significant reduction (P < 0.05) in the number of infected chickens and in the number of SE in the cecal contents was observed at 10 wk of age in Trial 2. The enrofloxacin treatment did not increase opportunistic colonization by SE due to the use of the antibiotic in either trial. The plasma and intestinal immunological responses were not significant at the early age (up to 12 wk) of the birds. The use of enrofloxacin, followed by NAGF, could aid the elimination of SE from young chicks persistently infected at an early age. The combined treatment, compared with enrofloxacin alone, protected chickens from reinfection by 40%.

Combined effect of antibiotic and competitive exclusion treatment on Salmonella enteritidis fecal shedding in molted laying hens

Salmonella Enteritidis is an important pathogen for the layer industry, primarily because of its ability to infect hens and ultimately contaminate egg contents. Studies have shown that stress situations, such as flock recycling (induced molting), can increase Salmonella Enteritidis problems in the flock. The present study examined the effect of antibiotic treatment and competitive exclusion (CE) on Salmonella Enteritidis shedding in the period following molt and 14-day feed withdrawal. In two separate trials, 48 birds after molt and feed withdrawal were divided into one group that was treated for 10 days with enrofloxacin in water followed by administration of CE culture and a group that was left untreated. Salmonella Enteritidis shedding was significantly reduced in the antibiotic-CE group. The Salmonella Enteritidis shedding rate was 33 and 25% in untreated birds versus 4 and 0% in the enrofloxacin-CE group on the two test days. These results indicate that treatment of Salmonella Enteritidis-positive laying hens after molting with enrofloxacin and CE culture can substantially reduce Salmonella Enteritidis problems due to molting and would be a possible alternative to diverting eggs for pasteurization or slaughtering the infected flock. Possible development of bacterial resistance in conjunction with antibiotic use is also discussed.

The use of competitive exclusion in broilers to reduce the level of Salmonella contamination on the farm and at the processing plant

The effect of a competitive exclusion (CE) product, Broilact, on Salmonella contamination of broiler chickens was studied on the farm and at the processing plant. In the first part of the study, two flocks per week, a CE-treated and an untreated control flock, were placed in similar broiler houses. The CE treatment was administered in the hatchery using a modified spray vaccination cabinet. Salmonella was analyzed from the paper pads of the transport boxes on arrival at the farm and from fecal samples taken 2 wk before slaughter. The results of Salmonella sampling were received for 67 flocks. The other 141 flocks of the company that were reared during the trial period were also sampled for Salmonella and the results were compared to those of treatment and control groups. Broiler performance, including mortality, weight, and feed conversion, was recorded for the trial flocks. In the second part of the study, Salmonella contamination of neck skin samples taken at the processing plant from 18 CE-treated and 28 control flocks was compared. The Broilact-treatment significantly reduced Salmonella contamination both on the farm and at the processing plant. At the level of the farm, the percentage of Salmonella-positive flocks was essentially the same in the control flocks and in other flocks reared during the trial period. An improvement in broiler performance was indicated, although the difference was not significant.