Avilamycin is a feed antibiotic active against grampositive bacteria i
n the alimentary tract of farm animals. The aim of this study was to s
pecify effect of avilamycin at 8 mg/l on in vitro fermentation of carb
ohydrates in the rumen fluid taken from fistulated wethers. Incubation
s were performed anaerobically at 39 degrees C in serum bottles closed
with Bunsen valves or hermetically closed with rubber bungs. Avilamyc
in significantly (P < 0.025) increased molar percentage of propionate
and decreased that of acetate in cultures supplied with starch, cellul
ose, hemicellulose and pectin. Avilamycin decreased the production of
lactic acid (P < 0.001) from sucrose and starch at low pH by 27.9%. Th
e production of methane and methane concentration in the headspace gas
were influenced to a very small extent. Generally, effects of avilamy
cin on rumen in vitro fermentation resembles ruminal effects of ionoph
ores and other grampositive antibiotics. Contrary to ionophores, avila
mycin-related shifts in fermentation stoichiometry are less pronounced
and do not include inhibition of methanogenesis.