Protection of chicks against Salmonella infantis infection induced by strict anaerobically cultured intestinal microflora.

In two experiments newly hatched broilers were orally inoculated either with intestinal microfloras cultured under different conditions or with a suspension of intestinal homogenate and challenged with high doses (3 X 10(5) c.f.u. per chick) of Salmonella infantis organisms. Inocula were prepared from intestinal material of mature SPF WL hens under aerobic or strictly anaerobic conditions (less than 5 ppm oxygen), and protected against atmospheric oxygen during storage. A very significant reduction of the number of Salmonella infantis bacteria in caecal content was achieved one and two weeks after challenge in those groups of chicks which were inoculated with anaerobically cultured flora or with intestinal homogenate. In order to induce protection, obligate anaerobes had to be accompanied by facultative anaerobes. Amprolium or Monensin dit not interfere with protection. Protection induced by intestinal microflora depends on anaerobiosis during preparation, culturing, storage, and application of the protective bacteria. Starvation on the first day of life appeared to have a negative effect on protection.