The effect of p-hydroxybenzoic acid (HBA), syringic acid (SYA) and yeast culture (YS) on rumen fermentation in vitro has been investigated. Meadow hay was used as a substrate and rumen fluid as an inocula. The yeast culture Levucel contained 5x10s yeast cells Saccharomyces cerevisiae per 1 g of dry matter and was used in the amount of 0.5 g/1 of the medium. The following combinations of additives were used: hay without additive, hay + YS, hay with 1, 5 or 10 mmol HBA or SYA, and hay + YS with 1, 5 or 10 mmol HBA or SYA. The test tubes were incubated for 96 hours at 39 °C. The results showed that 1 mmol HBA had a significant effect on yeast efficacy. This was manifested in the increased degradability of hay dry matter (P<0.05) and enhanced total gas production (P<0.05). SYA in the same amount combined with yeast had a similar effect on gas production (P<0.05), but hay dry matter degradability was not affected. The results showed a slight effect of phenolic acids and yeast culture on hay rumen fermentation in vitro.
Our experiments on metabolic processes in the rumen were performed on sixteen 5-month-old lambs divided into 4 groups (defaunated - D, totally refaunated - T, partially refaunated - P and intact - 1). The absence or presence of protozoa in the rumen did not significantly affect the pH values. The greatest differences in NH3 concentration in the rumen before feeding were found between the T and D group (P<0.05). The animals of the T and I groups had higher NH3 concentrations than the D and P groups 1-5 hours after feeding (P<0.05 to PcO.OOl). Blood urea concentrations before and after feeding were significantly higher in the group I compared to the other groups (P<0.05 to PcO.OOl). Significant differences in the total nitrogen in rumen fluid were only found between groups D and I. The values of protozoan nitrogen in the rumen and their mutual relationship among the groups could be expressed by the following ratios: I>T>P>D. Proportions of the values of bacterial nitrogen followed in this order: D>P>T>I. The animals in group D had a significantly higher level of residual nitrogen than those in the other groups (P<0.05).