NUMBERS AND CHARACTERISTICS OF LACTATE UTILIZING ORGANISMS IN THE RUMEN OF CATTLE

Abstract

24 strains of propionic acid-producing bacteria were isolated from the rumen of cattle, 7 strains were cultured from different types of hay, and 4 strains were recovered from soil samples. They resemble Propionibacterium acnes provided that the descr. of this sp. be modified to include lactate utilization. The numbers found in soil suggest that these organisms are widespread in nature, and the relatively large numbers in hay indicate that the latter may be a particularly favorable habitat. The isolated propionibacteria can grow rapidly at the expense of constituents in hay and grain and produce considerable amts. of acetic and propionic acids in cultures. These findings, together with the large numbers and consistent isolation of these bacteria from the rumen fluid of cattle, suggest an active role in the formation of propionic and acetic acids in the rumen, though the occurrence of such large numbers in hay makes it questionable whether the rumen is the site of most active growth.