Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2006
Publication Date: 12/1/2006
Citation: Murase, T., Chiba, K., Sato, T., Otsuki, K., Holt, P.S. 2006. Effects of different molting procedures on incidence of salmonella infection in flocks naturally contaminated laying hens in a commercial egg-producing farm by detection of yolk antibodies to salmonella in eggs. Journal of Food Protection.69:2883-2888 Interpretive Summary: An indirect enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies in egg yolks directed against different Salmonella serovars (strains) found in commercial layer flocks. Using bacterial cell wall components extracted from the different representative Salmonella strains, ELISA’s were run on yolks from these commercial hens. In hens vaccinated with killed S. enteritidis (SE), 39/40 yolks showed positive in the ELISA for SE as well as for other serovars, indicating the crossreactivity of bacterial components between Salmonella. An increase in the Salmonella positive ELISA was observed in yolks obtained from hens molted via feed withdrawal indicating that this procedure increased the incidence of Salmonella infection in these birds. Similar increases were not observed in yolks from hens molted via feeding wheat bran providing further evidence that this molting procedure will not exacerbate Salmonella problems in commercial flocks.
Technical Abstract: Indirect enzyme-linked immonosorbent assays (ELISAs) have been applied to detect immunoglobulin Y antibodies to different serotypes of Salmonella in the yolks of chicken eggs, using heat-extracted antigens of Salmonella enterica serotypes Agona (SA), Cerro (SC), Enteritidis (SE), Montevideo (SM), and Putten (SP). Egg yolk samples examined were classified as positive if their ELISA absorbance values exceeded the value for eggs from the specific-pathogen-free flocks by more than 2 standard deviations. Of 30 egg yolk samples from 3 flocks vaccinated with a killed SE vaccine, 29 were antibody positive using the ELISA for SE antigen. Four to 29 of the 29 yolk samples showed positive results for the other serovars, although the absorbance values for SE were higher than those obtained for the other serotypes in each of the yolk samples. All 30 yolks from 3 flocks that were not administered any SE vaccines were found to be antibody negative for SE and 2 samples were determined to be positive for CE. Thirty-nine or 40 eggs were obtained from each of 4 layer flocks in a commercial egg production farm where the laying houses were naturally contaminated with SA, SC, SM, SP, Salmonella serovar Infantis (SI), and untypeable strains. The ELISA absorbance values for (SM) in the egg yolks obtained from 2 flocks molted through feed withdrawal at the time when the birds restarted laying were significantly (p<0.05) higher than those observed in yolks obtained before molt. In the egg yolks from the other 2 flocks that were molted through wheat bran diet, there was no significant difference between the absorbance values before and after the molt. The observations in the present study provide further evidence to suggest that the molt through the wheat bran diet can reduce the risk for Salmonella problems in a commercial egg-producing setting.