| The objective of this study was to evaluate the effect of copper sources and concentrations on ruminal nutrient metabolism of steers in a 4×4 Latin square design .using two copper sources (copper DL-methionate and copper rumen by-pass) at four concentrations (0,8,16,24mg/kg) .Four steers weighed 420,aged 2.5~3,fitted permanent cannulate in the rumen, and were individually fed mixed ratio including concentration and com straw .Copper sources and concentrations had no significant effect on ruminal fluid pH value and NH3-N concentration (P>0.05). The supplementation of copper-methionate had passive effect on the degradability of corn straw in rumen.24mg/kg copper methionate decreased ruminal DM,OM,NDF,ADF degradability of com straw by 14.58%,16.38%,18.82%,26.35% (P<0.05),but copper rumen by-pass had no significant effect on celluloce degradability of corn straw(P>0.05).There were negative effect on the DM,OM degradability of soybean mea1.8mg/kg copper -methionate significantly decreased DM,CP degradability of soybean meal by 13.81%,23.34% (P<0.05).16 and 24mg/kg rumen by-pass copper decreased DM,OM degradability of soybean meal by 18.32%,33.16% and 20.21%,40.03% (P<0.05 ) respectively. The supplementation of copper sources and concentrations had slightly passive effect on ruminal fluid VFA and the production of rumen microbial protein(P>0.05) .These results showed that 8mg/kg rumen by-pass copper had better effect on ruminant metabolism in this studying conditions.
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