Effect of food protein supplements on Salmonella enteritidis infection and prevention in laying hens

Reduction of intestinal colonization of Salmonella enteritidis (SE) during the grow-out period is crucial to provide safer eggs, minimize economic losses, and reduce the spread of human salmonellosis. In the search for novel elimination and prevention methods based on feed supplementation, the effects of feed supplemented with nonimmunized egg yolk powder (did not contain anti-S. enteritidis antibodies), immunized egg yolk powder (with anti-S. enteritidis antibodies), egg yolk proteins, egg white, and skim milk powder were examined on laying hens. In the elimination study, the chickens were orally infected with SE then given a supplemented feed of 5, 10, or 15% (wt/wt) of each of the test samples. Fecal samples tested weekly showed an absence of SE after the first week of feeding nonimmunized egg yolk powder and a gradual decrease with the other samples. In the prevention study, Salmonella-free chickens were fed the supplemented feed for 4 wk and then infected orally. Fecal samples tested for 4 wk showed that SE was prevented from colonizing the intestinal tract throughout the test period by nonimmunized egg yolk powder, whereas the other samples only delayed the colonization. None of the fed supplements disrupted the balance of the intestinal microflora, and the counts in the feces remained constant. These results show that the administration of only 5.0% (wt/wt) of nonimmunized egg yolk powder can eliminate and prevent SE colonization in laying hens with no adverse effects. Furthermore, the present results indicate that hen egg yolk contains novel anti-adhesive or immunomodulatory components that may act to prevent SE infection.