Abstract: In order to research the effects of nicotinic acid and riboflavin duodenal infulsion on dry matter intake,milk production and blood parameters in dairy cows,five primiparous Chinese Holstein cows fitted with duodenal cannulas were arranged in a 5×5 Latin square design for five groups as control check (water,5 L/d),nicotinic acid(3 g/d),riboflavin(0.3 g/d),nicotinic acid and riboflavin blend(nicotinic acid 3 g/d + riboflavin 0.3 g/d)and B-vitamin blend(nicotinic acid 3 g/d + riboflavin 0.3 g/d+thiamine 0.03 g/d +pantothenic acid 0.42 g/d +pyridoxine 0.03 g/d +biotin 0.04 g/d +folic Acid 0.04 g/d).The results showed that the dry matter intake and milk production were improved significantly by nicotinic acid and riboflavin blend and B-vitamin blend(P<0.05),but with no effect of nicotinic acid or riboflavin(P>0.05).There were no effects of nicotinic acid on red blood cells and hemoglobin(P>0.05),as well as riboflavin on hemoglobin,but red blood cells were decreased by riboflavin. For nicotinic acid and riboflavin blend,both of red blood cells and hemoglobin were decreased(P<0.05),inversely improved by B-vitamin blend(P<0.05).All the vitamin treatments had no effects on other red blood cellsparameters and platelet parameters(P>0.05),but the platelet tended to increase. It suggested that nicotinic acid and riboflavin supplement at the same time can improve performance,and red blood cells and hemoglobin may be improved by B-vitamin blend. Duodenal infusion of nicotinic acid,riboflavin,nicotinic acid and riboflavin blend,B-vitamin had no adverse effect on milk flavor. Milk from cows infused nicotinic acid and riboflavin blend,B-vitamin blend into duodenum had better flavor than milk from control cows.

Key words: nicotinic acid; riboflavin; performance; blood parameters; duodenal infusion; dairy cows