An Investigation into the Effect of Sampling Time, Cow Factors and Feeding Management Factors on Diurnal Variation in Milk Urea Nitrogen

Abstract

As part of the process of developing criteria by which to accurately interpret milk urea nitrogen (MUN) measurements and correctly use this information in the nutritional management of dairy herds, it is important to understand how certain factors related to sample collection, sample type and sample handling may effect these measurements. Research by Gustaffson and Palmquist (J. Dairy Sci. 76:4 75-484) and by Carlsson and Bergstrom (Acta Vet. Scand. 35:67-77) has demonstrated that there may be considerable diurnal variation in MUN levels, with peak MUN levels being reached 3 to 5 hours post-feeding. Although feeding schedules were identified as a major factor influencing diurnal variation, it is possible that other factors may be involved. Herd level and cow level factors such as the rations fed, feeding frequency, feeding management system, stage of lactation, parity and level of production may each play a part in influencing diurnal variation in MUN levels.