[Effect of the polyether antibiotic monensin on rumen fermentation in fattening bulls during the feeding of rations rich in sugar beets].

In an experiment with six fattening bulls the influence of the polyether antibiotic "Monensin" (200 mg/animal and day) on the rumen physiologic parameters before and one, two, three and six hours resp. after the feeding of rations rich in dried sugar beet was investigated. The parameters of rumen fermentation are significantly influenced by the time of rumen fluid sampling and by the quota of dried sugar beet in the concentrated feed (40 and 80% resp.). The effect of "Monensin" supplementation was a narrowing of the acetate: propionate proportion in the rumen fluid over the complete period of the experiment. The molar butyrate quota was distinctly diminished in comparison with earlier feeding experiments with fattening bulls. This effect is caused by the relatively higher values of the butyric acid content in the rumen fluid, which is due to the high quota of dried sugar beet in the concentrated feed.