The Influence of Penicillin and Oxytetracycline in the Ration on Mortality, Lesions and Predominating Microflora in Experimental CRD

Abstract

ABSTRACT INTRODUCTION THE efficacy of oral treatment or prophylaxis of CRD with antibiotics or other chemotherapeutic agents has been evaluated by a number of investigators. Lowered mortality, greater gains, improved feed conversion and egg production, as compared with controls, have been reported for CRD infected birds receiving oxytetracycline 1 treatment (Van Roekel et al., 1952; Peterson et al., 1954; Lecce and Sperling, 1955; and Olesiuk et al., 1957). As an example, Peterson and co-workers (1954) reported a reduction in mortality due to CRD from 23.9% to 10.5% in field trials involving 36,000 birds when this antibiotic was fed at 100 gm. per ton of ration. Improvements in weight gain and feed conversion were also noted. On the other hand, no benefit due to the feeding of oxytetracycline was noted in a report by Fahey and Crawley (1955). Although there have been suggestions from field work that penicillin may be beneficial in CRD . . .