Manipulation of the crop and intestinal flora of the newly hatched chick.

The ceca of newly hatched chicks obtained either from commercial hatcheries or from a carefully controlled experimental hatchery have been shown to contain high numbers of a variety of microorganisms. Fecal streptococci, clostridia, enterobacteria, pediococci, and occasionally Pseudomonas aeruginosa have all been isolated, but never lactobacilli. After the chick has been on feed for 1 day, the numbers of lactobacilli in the crops and ceca are quite variable; by the 3rd day, however, large numbers are present throughout the alimentary tract. Lactobacilli could be established after 1 day by incorporating them in the feed or by treating the chicks with 0.5 ml of a broth culture. Spraying the eggs before hatching did not lead to their early establishment. Lactobacilli given alone to the newly hatched chick failed to prevent the establishment of Salmonella. However, when the chicks were given a complex mixture of facultative anaerobes and anaerobes which had been isolated from an adult bird, cecal colonization with Salmonella was prevented. The possible importance of the facultative anaerobes, particularly Streptococcus faecalis, in lowering the redox potential to encourage the growth of the anaerobes is discussed.