Effect of plant oils and organic acids on rumen fermentation in vitro.

We determined the effect of plant oils (rapeseed, sunflower, linseed) and organic acids (aspartic and malic) on the fermentation of diet consisting of hay, barley and sugar beet molasses. Rumen fluid was collected from two sheep (Slovak Merino) fed with the same diet twice daily. Mixed rumen microorganisms were incubated in fermentation fluid, which contained rumen fluid and Mc Dougall's buffer. All supplemented diets significantly increased pH, molar proportion of propionate, and numerically decreased methane production. Lactate production was also decreased significantly (except with malate). Incorporation of plant oils into aspartate- and malate-treated incubations negated the decrease of butyrate, lactate and the increase of pH and ammonia with malate treatment, as well as in vitro dry matter digestibility and pH with aspartate treatment. The effect of combined additives on methane production and molar proportion of propionate was lower compared with additives supplemented separately. Combination of additives had no additive effect on rumen fermentation. All additives decreased total protozoan counts in rumen fluid.