Abstract
During the 1962 pasture season, 203 dairy and beef animals and 445 sheep were used in controlled pasture bloat studies in which the effects of a bolus containing a combination of streptomycin sulfate, tylosin phosphate, erythromycin thiocyanate and procaine penicillin were evaluated. The data obtained from cattle show that the initial administration of either one, two, or three boluses reduced bloat for 3–4 weeks. Administration of either one or two boluses 6 weeks after the first boluses were given usually effected a reduction in bloat for about 1 week. Average weight gains were greater (0.14 lb. per animal daily) in 70 animals receiving antibiotic boluses than in 44 controls. In sheep, the initial administration of one-half bolus reduced bloat for about 3–4 weeks, whereas administration of the same dosage 4 weeks after the first bolus effected no reduction. Wool loss from the dorsal surface of the body was noted in about 75% of the treated group in one flock. No wool loss occurred in the control group or in the other treated sheep. Studies with four rumen fistulated steers demonstrated that the majority of the boluses, when administered by balling gun, are deposited initially in the anterior dorsal blind sac of the rumen. Observations on these fistulated steers and four intact steers showed that most of the boluses subsequently migrate to the reticulum. The bolus, gradually dissipated by erosion, has a half-life (weight basis) of approximately 2 months; however, very little antibiotic activity remains in the bolus after 6 weeks (Eli Lilly and Co., 1962, unpublished). Preliminary observations suggest that oral administration of potassium levopropylcillin reduces the incidence and severity of bloat for a substantially longer period of time when fed singly than did other antibiotics that have been tested. Copyright © 1964. American Society of Animal Science . Copyright 1964 by American Society of Animal Science