Abstract: The method of rumen fermentation in vitro was used to study the effect of various supplementary feeds, rumen micro-organisms, incubation time on cattle rumen hydrogenation. The results showed that 64.20% variation of NH₃-N was affected by incubation time, which was the main effect of variation of NH₃-N; various concentrate supplement, rumen micro-organisms and incubation time had significantly different effects on various VFA components; the interaction between incubation time and rumen micro-organisms affected propanoic acid, isobutyric acid, butyric acid significantly (variances of interaction effect were 43.32**,1.56** and 2.87**, respectively). Acetic acid, isovaleric acid and valeric acid were free from the impaction of rumen micro-organisms, incubation time and different supplement. The highest concentration of NH₃-N (19.49 mg·mL^-1) was observed when extruded soybean was used as supplement. Different supplement, incubation time and interaction between them significantly affected the concentration of stearic acid (totally 77.76% variation was attributed to these three components). The remarkable influence on the content of stearic acid was produced only at specific time in rumen microflora. Concentration of linoleic acid (18∶2) was impacted only by different rumen microflora. Different material, incubation time and interaction in rumen microflora significantly affected the concentration of trans-oleic acid (18∶1) and linolenic acid (18∶3).

Key words: concentrate supplement, incubation time, microflora, hydrogenation, PUFA