THE EFFECT OF AVILAMYCIN ON IN-VITRO RUMI NAL FERMENTATION OF CARBOHYDRATES

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.