Abstract: Abstract: Three rumen-fistulated hybrid yellow cattle were randomly assigned according to a 3×3 Latin square design to investigate effects of supplementation oil in concentrates on pH, NH3-N, VFA and rumen microflora. The dietary treatments were 65% rough and 35% concentrate-based, containing 0 (control), 4% soybeam oil (soybean oil treatment) and 4% linseed oil (linseed oil treatment) of DMI, respectively. The experiment was conducted for three periods, each period lasting 21 days. The results indicated that ruminal pH value was not significantly affected by supplementing oil (P＞0.05). NH3-N concentrates in control and linseed oil treatment were significantly higher than soybean oil treatment (P<0.05). Compared with control group, acetate, propionate, butyrate and total VFA concentration, total viable bacteria, proteolytic bacteria, cellulytic bacteria and protozoa in soybean oil and linseed oil treatments were dramatically lower than the control group. However, there were not significant differences on acetate to propionate ratio and amylolytic bacteria by supplementing oil.

Key words: Soybean oil, Linseed oil, Rumen ecology, Bacteria, Protozoa,