Nutritional and management factors associated with milk urea nitrogen levels in maritime dairy cattle fed under commercial conditions

Controlled feeding trials have demonstrated associations between milk urea nitrogen (MUN) and protein intake and between MUN and fermentable energy intake. The variation in the total amount of ingested protein had only a slight effect on MUN levels when the ratio between protein and energy was held constant. Most trials have been based on a relatively small number of cows, frequently without access to pasture. Results from a large scale observational study involving Prince Edward Island (PEI) dairy herds would clarify how nutritional and other factors affect MUN in cows maintained under commercial conditions on PEI.

Between October 1999 and January 2001, 83 dairy herds from PEI and 9 dairy herds from Nova Scotia were enrolled in this study. Herds evaluated during the grazing period were divided into two groups: intensive grazing managers and extensive grazing managers. The same herds were evaluated during the confinement period and were classified as being either total mixed ration herds or component fed herds. The study included four data collection periods (minimum of two farm visits and two telephone conversations). (Abstract shortened by UMI.).