[The effect of monensin on the fermentation of feed with different proportions of hay and concentrate in an artificial rumen (rumen simulation technic)].

An experiment was conducted with rumen pouch (RUSITEC--Rumen Simulation Technique). In four fermentation vessels (V), percent proportions of hay and barley were as follows: V1--40:60, V2 - 60:40, V3--80:20 and V4--100:0. Every day 5 mg of monensin dissolved in 1 ml 96% ethanol were added to each fermentation vessel. All diets were isonitrogenous, and after an addition of urea the crude protein (CP) content made 13% in each diet. The experiment lasted 12 days: so called steady state period took the first six days when the fermentation conditions were stabilized. Monensin reduced dry matter digestibility, production of total volatile fatty acids, acetic acid, n-butyric and isovaleric acids and acetate: propionate proportion, and it increased the production of propionic and n-valeric acids. The production of methane and CO2 decreased. The higher proportion of hay in diets decreased dry matter digestibility, digestibility of detergent fibre, total and individual volatile fatty acids, CO2, methane energy yield of volatile fatty acids (E), glucose utilization, production of adenosine triphosphate and production of fermented hexoses. The production, utilization and recovery of metabolic hydrogen also decreased. The effectiveness of microbial matter synthesis (YATP = 11.3) was highest during the fermentation of feed containing 60% hay and 40% barley.