为了研究日粮阴阳离子平衡（dietary cation-anion balance，DCAB）对泌乳中期奶牛血液生理指标和泌乳性能的影响，本试验选择12头体况相近的泌乳中期荷斯坦奶牛，采用随机区组设计分成4组，分别饲喂4种不同DCAB日粮，A组(对照组)DCAB为200 mEq/kg DM，B组DCAB为250 mEq/kg DM，C组DCAB为300 mEq/kg DM，D组DCAB为400 mEq/kg DM，试验期为21 d。结果表明：增加DCAB可显著增强奶牛血液的缓冲能力和运氧能力，且奶牛血液pH和实际碳酸氢盐含量随DCAB的升高而增加（P<0.05）。B组的动脉血二氧化碳分压与A组之间没有显著差异（P>0.05），而与C、D组之间有显著差异（P<0.05）；C组的血液二氧化碳总量和碱贮含量较A组增加，均达到了极显著水平（P<0.01）；同时，试验也表明高DCAB水平的日粮能提高奶牛的泌乳性能，但差异不显著（P>0.05）。综合考虑奶牛血液生理指标和泌乳性能，在奶牛泌乳中期DCAB为300 mEq/kg DM时效果为佳。

The experiment was conducted to study the effects of dietary cation-anion balance (DCAB) on blood physiological indices and performance in the dairy cows in mid-lactation. Twelve dairy cows in mid-lactation period were used in the experiment and divided into 4 groups randomly with 3 cows in each group to determine the optimum level of DCAB. The experiment lasted for 21 days, and four levels of DCAB were as follows: group A (DCAB of 200 mEq/kg DM), group B (DCAB of 250 mEq/kg DM), group C (DCAB of 300 mEq/kg DM), and group D (DCAB of 400 mEq/kg DM). The results showed as follows: abilities of blood buffer and O2 transport of dairy cows were increased with DCAB increasing. Blood pH and content of HCO-3 were increased predominantly as a result of DCAB increase (P<0.05). The partial pressure of CO2 in arterial blood in group B had significant difference in comparison with that in groups C and D (P<0.05). Group C had significant influence on TCO2 and blood base excess in comparison with group A (P<0.01). The increase of DCAB affected lactation performance, but not significantly (P>0.05). Considering of the results above, a better effect of diary cows was observed in group C with DCAB of 300 mEq/kg DM.［Chinese Journal of Animal Nutrition, 2010，22（4）:1096-1100］