Persistence of lactobacilli and streptococci in the bovine rumen during penicillin administration.

At the 1957 Conference on Rumen Function, Barrentine et al. (1958) and Emery et al. (1958) presented reports supporting the use of penicillin for the control of bloat in cattle. At the same conference, Johnson et al. (1958) and Smith and Emery (1958) reported that the administration of 50 to 100 mg of penicillin daily reduced the incidence of pasture bloat, but this control was not effective after 7 to 9 days of treatment. Johns (1958) found that, after penicillin had been given every 2 days for some 12 doses, the inhibiting effect on rumen fermentation disappeared. Little information is available to explain the mode of action of this prophylactic measure or the disappearance of the inhibiting effect after continued administration. Smith and Emery (1958) detected a "penicillin destroying principle" in Seitz-filtered rumen fluid of penicillintreated cattle after 1 week of treatment. The present study is an attempt to determine the effect of penicillin upon the lactobacilli, streptococci, and coliform bacteria in the rumens of fistulated steers grazed on Ladino clover. The first two of the bacterial groups were selected for their possible role in the bloat process, in view of the report of Perry and Briggs (1957) that the "lactobacilli constitute a major component of the bovine ruminal microflora .. . " and that of Dain et al. (1956) that Streptococcus bovis may be important in the production of the slime often associated with bloat. The coliform bacteria that were isolated were assayed for their possible role in the destruction of penicillin since Harper (1943) has reported that sterile filtrates of coliform bacteria were capable of penicillin inactivation. Bondi and Dietz (1944) designated the penicillin destroying agent produced by paracolon bacilli as penicillinase.