EFFECT OF IONOPHORES ON IN IN-VITRO CECAL FERMENTATION IN RABBITS

Experiments were carried out at Uhrineves, Czech Republic, in 1995 and 1996 to evaluate the effect of salinomycin, monensin, lasalocid and m aduramicin on in vitro rabbit caecal fermentation. In cultures supplie d with starch, hemicellulose and pectin, all ionophores in the range o f concentrations tested (1-10 mu g/ml) stimulated methanogenesis. Iono phores at 5 mu g/ml increased the production of methane by 26-35 % and decreased the production of acetate (P < 0.05). Significantly more ac etate was produced in mixotrophic acetogenic cultures of caecal micro- organisms with glucose (2 mg/ml) under hydrogen atmosphere than under nitrogen. The H-2-dependent formation of acetate was blocked in cultur es with ionophores. The stimulation of methanogenesis by salinomycin, monensin, lasalocid and maduramicin can thus be related to the inhibit ion of acetogenesis, which is an alternative method of H-2 utilization in the rabbit caecum.