Rumen fermentative characteristic is useful indicators of the quality of ruminant feed stuffs and diets. An in vitro rumen fermentation experiment was therefore carried out to compare fermentation patterns among three forage sources. These were whole crop barley (WCBS), Italian ryegrass silage (IRGS) and rice straw silages (RSS). Rice straw (RS) was the control, making the treatments 4 in total. Forages were randomly allocated to serum bottles. The incubation times were arranged 0, 3, 6, 9, 12, 24, 48 and 72h at $39^{circ}C$, respectively. Each forage source was replicated 3 times per incubation time. At each sampling time, total gas and pH were measured, whilst individual volatile fatty acids (VFAs), total volatile fatty acids (TVFAs) and ammonia nitrogen ($NH_3$-N) were determined later after storing samples at $-20^{circ}C$. Acetate: Propionate ratio (A/P) was then calculated. Forage source had a significant effect (P<0.001) on pH and $NH_3$-N. RSS maintained higher pH values than the rest of the forage sources. A decreasing pH trend with increased time of incubation, in agreement with literature, was observed for all forage sources. WCBS recorded $NH_3$-N values higher than all the other treatments. Total gas, individual and total VFA and A/P ratio were not affected by forage source. However, there was a significant difference in all parameters (p<0.05) among forage sources at sampling periods at 3 to 72h. Therefore, the present results indicating that WCBS, IRGS, RS and RSS maintained in vitro rumen pH above the critical value. Also, WCBS produced the highest NH3-N and on this merit could be of better nutritive value, in vivo, in the ruminant.