Effects of Parity, Days in Milk, Milk Production and Milk Components on Milk Urea Nitrogen in Chinese Holstein

摘要

The objectives of this study were to evaluate the effects of parity, Days in Milk (DIM), milk production and components on Milk Urea Nitrogen (MUN) concentration in Chinese Holstein. About 6500 lactating cows of 20 dairy farms from Ningxia, Shanghai and Beijing participated in this study. Finally, 29414 records from Jan 2008-July 2009 were analyzed. The milk components and MUN concentration were measured using a Fossomatic 4000 Milkoscan Analyzer at the Shanghai Milk Quality Laboratory. The mean MUN concentration was 19.4 mg dL-1 and the lowest value appeared in the third and greater lactation. The concentration of MUN reached the highest at 90-120 DIM and began to go down approximately 120 DIM. A positive relationship existed between MUN and milk production, while negative relationship with milk protein and milk fat percentage were observed. Based on the results from this study, MUN concentration should be interpreted in association with parity, DIM, milk production and composition when MUN was regarded as a management tool to evaluate the efficiency of nitrogen utilization for dairy cows in China.