Abstract: The effect of three different level of ratio of protein to energy in ration on growth performance and biochemical serum indexes of holstein male calves was examined.The high level ratio of protein to energy in ration showed a significant effect on the average total gain and average daily gain than the low one（P<0.05）,but the medium one had no difference compared to the fomer two（P>0.05）.In general, the data suggested that the high level of ratio of protein to energy in ration had the best feed efficiency and economic efficiency in the experiment.Though different diets had some effects on blood indexes,the numerical values were all in the normal physiological range.The results indicated that serum total protein and glucose and serum ureanitrogen tended to increase but serum total fat of the low one reduced after taking the diets.

Key words: protein/energy; holstein male calf; growth performance; biochemical serum