关键词: 蛋白能量比; 中国荷斯坦犊牛; 饲料效率; 表观消化率

Abstract: This study was conducted to evaluate the effects of different ratios of dietary CP to digestible energy （CP∶DE） on growth performance and feed efficiency of 3 to 5 months Chinese Holstein calves. Thirty weaned completely Chinese Holstein calves at 70 d were divided into 3 groups in a randomized complete block design,(labeled as groups A,B and C) and randomly assigned to one of three treatment rations that the CP∶DE ratios were 50.0,52.0 and 54.9 g of CP per Mcal DE，respectively. Treatment rations imposed for 90 d and the quantity of treatment ration offered to each calf was adjusted per 10 days to allow approximately 0.80 kg/d gain. Average daily gain(ADG) did not differ between the treatment rations 0.83,0.80,0.81 kg/d, low to highest CP∶DE ratio, respectively. Feed efficiency improved linearly with increasing CP∶DE ratios, 4.29,4.24,3.96 kg/d, respectively but were not significantly difference. A trend toward linear increases in the apparent digestibility of DM and CP with increasing CP∶DE ratios and a trend toward linear decreases in the apparent digestibility of DM and OM. After the third months, the apparent digestibility of P went steadily. The levels of plasma urea N increased with increasing CP∶DE ratios. Considered linear effects in feed efficiency，and change of ADG and nutrient apparent digestibility et,al. In this experiment, the diet of CP∶DE ratios was 50.0∶1 could meet needs of the 3～5 months China Holstein calves gaining 0.80 kg/d.

Key words: protein energy ratio; Chinese Holstein calves; feed efficiency; apparent digestibility