Abstract: The effects of rumen fermentation by adding inorganic phosphorus in vitro were studied,Concentration of inorganic phosphorus were 0,30,60,90,120,150,200,250,300 and 350 mg/L. The pH and volatile fatty acid (VFA) of 48 h fermentation in vitro were measured. The results as follows: Acetate,propionate,butyrate acid and total VFA production were significantly effected by the concentration of inorganic phosphorus(P＜0.05). Acetate,propionate,butyrate acid and total VFA production were the highest when the concentration of inorganic phosphorus was 200 mg/L. pH was significantly influenced by different inorganic phosphorus levels(P＜0.05). pH decreased when inorganic P levels increased(P＜0.05)and reached its minimum when inorganic phosphorus was 200 mg/L.In this experiment the optimum adding levels of inorganic phosphorus was 200 mg/L.

Key words: in vitro; inorganic phosphorus; pH; volatile fatty acid (VFA)