gramicidin-a and propionic-acid

Aibellin was administered in feed to goats (16 to 18 kg of BW) for 12 d. At 80 mg/d, the molar percentage of propionate in rumen fluid increased significantly in 8 d, and the effect lasted for as long as 10 d after administration ceased. Total VFA concentration, protozoa numbers, and NDF digestibility were not depressed significantly at this dosage but were reduced at 100 mg/d with little further increase in the molar percentage of propionate. Therefore, the optimal dosage of aibellin was 80 mg/d under our experimental conditions. In contrast, monensin (30 mg/d) and gramicidin D (60 mg/d) decreased total VFA concentration and protozoa numbers when supplemented to obtain molar percentages of propionate comparable to 80 mg/d of aibellin. From these results, aibellin may be easier and safer to use than monensin and gramicidin D to modify rumen fermentation.

Topics: Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Dietary Fiber; Digestion; Eukaryota; Fatty Acids, Volatile; Fermentation; Goats; Gramicidin; Monensin; Peptides; Propionates; Rumen

A new icosapeptide, aibellin, markedly modified rumen fermentation in vitro. Batch culture experiments with mixed rumen microorganisms showed that 12.5 to 25 mg/L of aibellin enhanced propionate production and reduced methanogenesis without significantly affecting production of total VFA, protozoal survival, or cellulose digestion. Aibellin had essentially the same effects in continuous culture with hay powder and concentrate. Monensin (5 mg/L) had similar effects on propionate production and methanogenesis, but total VFA, protozoa, and cellulolysis were decreased even by this low concentration of monensin. Commercially available peptide antibiotics also were compared with aibellin. Of the antibiotics examined, only graminicidin D (7.5 to 15 mg/L) enhanced propionate production and reduced methanogenesis. However, gramicidin D decreased total VFA, protozoa, and cellulolysis even at 7.5 mg/L. Alamethicin (7.5 to 15 mg/L), which resembles aibellin in its structure, did not increase propionate production but raised the percentage of propionate because of reduced production of total VFA. Alamethicin depressed 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.

Topics: Alamethicin; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Fatty Acids, Volatile; Fermentation; Goats; Gramicidin; Methane; Monensin; Peptides; Propionates; Rumen