EVALUATION OF A CHICK MORTALITY MODEL FOR PREDICTING THE CONSEQUENCES OF SALMONELLA-ENTERITIDIS INFECTIONS IN LAYING HENS

The effects of four domestic Salmonella enteritidis (SE) isolates were compared in experimentally infected chicks and laying hens. The pathogenicity of each strain for 1-day-old chicks was determined by recording postinoculation mortality. The effects of the SE strains on adult hens were measured in terms of changes in total egg production, the frequency of production of SE-contaminated eggs, the dissemination of SE to internal organs, and the elicitation of a specific antibody response. Significant differences in the consequences of infection with different SE strains were observed in mortality rates among chicks and in total egg production, the frequency of production of contaminated eggs, and the serum antibody response among laying hens. The usefulness of a chick mortality model for predicting the probable frequency of production of contaminated eggs by laying hens infected with particular SE strains was then further evaluated by infecting chicks and laying hens with four other field isolates of SE. Although significant differences between SE strains were observed in both chick mortality and the frequency of production of contaminated eggs by hens, a strong correlation between these two parameters was not evident.