Milk Urea Testing as a Tool to Monitor Reproductive Performance in Ontario Dairy Herds

摘要

Dairy herd improvement test-day data, including milk urea concentrations measured using infrared test method, were collected from 60 commercial Ontario Holstein dairy herds for a 13-mo period between Decem- ber 1, 1995, and December 31, 1996. The objective of the study was to describe, at the cow and the group level, the relationship between DHI milk urea concen- trations and reproductive performance in commercial dairy herds. When interpreted at the cow level, there was no asso- ciation between milk urea and the risk for pregnancy from an insemination occurring within the 45-d period preceding test day. However, a negative curvilinear re- lationship existed between milk urea and the risk for pregnancy from a first, second, or third insemination event occurring within the 45-d period following test day, with the odds for pregnancy being highest when the milk urea on the test day preceding the insemina- tion was either below 4.5 mmol/L or greater than 6.49 mmoim, compared with a concentration between 4.5 and 6.49 mmol/L. When interpreted at the group level, there was no association between group mean milk urea for cows between 50 and 180 DIM, and the group con- ception rate for cows receiving a first, second, or third insemination event in the 45-d period either preceding or following test day. Thus, while DHI milk urea mea- surements may be useful as a management tool to im- prove the efficiency of production or reduce nitrogen excretion, through helping to optimize the efficiency of protein utilization, they may have limited utility as a monitoring or diagnostic tool for reproductive perfor- manc e. The results of this study suggest that good fertil- ity may be achieved across a broad range of milk urea concentrations.