Generation times of Epidinium caudatum and Entodinium caudatum, determined in vitro by transferring at various time intervals.

Generation times were determined in vitro with a pure culture of Epidinium caudatum and a mixed culture of Epidinium caudatum and Entodinium caudatum. Measurement of logarithmic growth from a small inoculum for Epidinium caudatum alone, or in coculture, resulted in generation times of 30.8 and 19.5 h, respectively. Epidinium concentrations, either alone or in coculture, were maintained when cultures were transferred every 12 h; however, concentrations decreased rapidly with transfers at 4, 6, or 8 h. For Entodinium caudatum, a generation time of 16.3 h was obtained from measurement of logarithmic growth. Based on sequential transfer data at varying time intervals, Epidinium caudatum and Entodinium caudatum seem to be capable of doubling in approximately 12 to 13 h. These values are markedly less than those previously reported and help explain the ability of these protozoa to maintain themselves in the rumen.