Chicks (Gallus domesticus) were treated per os with 24-h-old anaerobic cultures of feces from mature chickens 1 day after hatching, challenged with Salmonella typhimurium in the drinking water 2 days later, and sacrificed on day 11 or 12; then the lower third of the intestinal tract was examined for salmonellae. Cultures of feces inoculated directly into the crop or added to the drinking water, even after holding at −70 C for 21 days, protected chicks against infection by S. typhimurium. Cultures serially subcultured daily up to four times were protective, and dilution to 1:80 in drinking water containing 4 % skim milk powder did not decrease their protective effect. Treated chicks were about 1000-fold more resistant to infection by Salmonella than untreated chicks.

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