Use of milk urea nitrogen to improve dairy cow diets.

The hypothesis of this field study was that providing farmers with information regarding their herd's milk urea nitrogen (MUN) would result in more accurate feed management and a change in MUN toward target values. All dairy herd bulk tanks (n = 1156) in the Maryland and Virginia Milk Producers' Cooperative were tested for MUN each month for six months ending in May 1999. Farmers (n = 454) who returned a survey were provided with the results of their MUN analysis each month along with interpretive information. Survey results indicated that most (89.5%) dairy farmers did not routinely use MUN prior to participating in the project, but most (88%) extension agents and nutritionists in the region recommended it. The average MUN across all farms in the study increased in the spring, but the increase was 0.52 mg/dl lower for farmers receiving MUN results than for those who did not participate in the program. Farmers who indicated they increased dietary crude protein (CP) due to low MUN started with MUN values that were 3 mg/dl below target but ended with target values. Farmers who indicated that they decreased CP due to high MUN began the project with high MUN but decreased it by 1 mg/dl compared to non-participating farmers. At the end of the project, 30% of farmers responding to a follow-up survey indicated they would use MUN analysis in the future. Providing MUN results and interpretive information to farmers was documented to change feeding practices and subsequent MUN results.