Studies on the Cecal Microflora of Commercial Broiler Chickens

A study was made of the cecal microflora isolated from broilers (5-week-old) reared under typical commercial husbandry conditions. Three hundred and twenty-five bacterial strains (randomly isolated from colonies representing 49 to 81% of the microscopic count) were isolated from cecal digesta of six animals on a rumen fluid roll tube medium (M98-5). Seventy-seven percent of these strains consisted of strict anaerobes: gram-negative, pleomorphic cocci (5.2%), Peptostreptococcus (1.5%), gram-positive rods (36.1% as Propionibacterium acnes and Eubacterium sp.), gram-negative rods (18.6% as Bacteroides clostridiiformis, B. hypermegas and B. fragilis) and sporeforming rods (15.7% as Clostridium sp.). Two types of facultatively anaerobic bacteria (gram-positive cocci and Escherichia coli) were also isolated and constituted 17.5% of the remaining flora. The distribution of the bacterial groups isolated from six cecal samples varied considerably. Data on the growth requirements of anaerobic strains indicated that many could be cultured in a simple medium consisting of an energy source, minerals, reducing agent, Trypticase, and yeast extract (or a vitamin mixture in place of yeast extract). The growth of some of these bacteria was also enhanced by CO(2) and rumen fluid. These preliminary data suggest that some of the more numerous anaerobes isolated from the chicken cecum may not require complex nutrients for growth and, in fact, may be nutritionally similar to rumen anaerobes.