EFFECTS OF AIBELLIN, A NOVEL PEPTIDE ANTIBIOTIC, ON RUMEN FERMENTATION IN-VITRO

A new icosapeptide, aibellin, markedly modified rumen fermentation in vitro. Batch culture experiments with mixed rumen microorganisms showe d that 12.5 to 25 mg/L of aibellin enhanced propionate production and reduced methanogenesis without significantly affecting production of t otal VFA, protozoal survival, or cellulose digestion. Aibellin had ess entially the same effects in continuous culture with hay powder and co ncentrate. Monensin (5 mg/L) had similar effects on propionate product ion and methanogenesis, but total VFA, protozoa, and cellulolysis were decreased even by this low concentration of monensin. Commercially av ailable peptide antibiotics also were compared with aibellin. Of the a ntibiotics examined, only graminicidin D (7.5 to 15 mg/L) enhanced pro pionate production and reduced methanogenesis. However, gramicidin D d ecreased total VFA, protozoa, and cellulolysis even at 7.5 mg/L. Alame thicin (7.5 to 15 mg/L), which resembles aibellin in its structure, di d not increase propionate production but raised the percentage of prop ionate because of reduced production of total VFA. Alamethicin depress ed methanogenesis but also decreased protozoal survival and cellulose digestion. These in vitro experiments indicate that aibellin could be a useful and potent modifier of rumen fermentation.