Abstract: [Objective] To explore the effects of probiotics on feed intake,weight gain,carcass rate and blood indexes of weaned calves. [Methods] Sixteen （60±5）day old Holstein calves were randomly divided into four groups CK group （basic diet +0% probiotics）,treatment group 1 （basic diet +1% probiotics）,treatment group 2 （basic diet +2% probiotics）,treatment group 3 （basic diet +3% probiotics）. The pre-trial period was 3 days,and the formal feeding was 42 days. [Results] Compared with CK group,the average daily feed intake of treatment group 1, treatment group 2 and treatment group 3 increased by 6.05%,7.44% and 7.91% respectively （P> 0.05）,the average daily gain increased by 7.11%,21.84% and 21.24% respectively （P< 0.05）, and the carcass rate increased by 6.78%,9.75% and 8.47% respectively （P< 0.05）. There was no significant difference in feed weight ratio between treatment group 1 and CK group （P> 0.05）, while treatment group 2 and treatment group 3 compared with CK group,The feed to weight ratio decreased significantly by 11.84% and 10.90% respectively（P< 0.05）.The contents of total protein,albumin and globulin in serum of weaned calves treated with different probiotics showed a significant increase trend （P < 0.05）,but there was no significant difference in urea nitrogen, creatinine and uric acid indexes （P> 0.05）. [Conclusion] Adding an appropriate amount of probiotics to the diet of weaned calves can promote the weight gain of calves,stimulate feeding, improve immunity,and integrate various indicators and feeding costs. The appropriate amount of probiotics is 2%.

Key words: weaned calves, probiotics, feed intake, growth performance, blood index