Abstract: In the condition of heat stress, dietary cationanion balance had a significantly effects on production and health of dairy cow. They can directly affect the balance of acid and base, metabolism of mineral matter, the level of enzyme and hormone. By this way, they can improve health condition, feed intake and production of dairy cow.75 middle lactation(104.8±12 DMI) China Holstein cows come from Anding Pengfeng dairy farm of Beijing were used in this experiment. These cows were randomly divided into five groups by similar parity, milk yield and weight into five treatment groups, every group were adjusted the DCAB value by providing with different level cationanion salt. Five group were group Ⅰ,Ⅱ,Ⅲ,Ⅳ and control group, the DCAB value of these group diets were 195.76, 186.68, 177.77, 166.94 and 239.12 m Eq/kg DM. The experimental stage were lasted 67 days, 7 days for test period beforehand and 60 days for test period. We change the DCAB value to study the effect of different DCAB value on the performance and blood chemistry of dairy cattle on the condition of heat stress. The results indicated that in the condition of heat stress, different DCAB value diet can influence the performance and the milk quality. Compared with control group, the milk yield of group Ⅰ and Ⅱ increased 1.6% and 0.8%, but the milk yield of group Ⅲ and Ⅳ decreased 2.2% and 1.7%, but the difference is not significant (P＞0.05). However, the milk fat rate, milk protein 〖JP2〗rate, lactose, total solids mass and somatic cell count were not significantly affected by change the DCAB value of the diets. Meanwhile, the concentration of nitric acid salt and nitrous acid salt in milk were not significantly affected by these diets(P＞0.05).

Key words: dietary cationanion balance; heatstress; dairy cow; productive performance