Utilization of milk urea concentration as a tool to evaluate dairy herd management

Abstract

The milk urea (MU) content variation was monitored in fourteen herds over a year to verify the reliability of this parameter as an indicator of the nutritional protein status of dairy cows. The relationships between MU concentrations and the nutritional value of the feed, pasture characteristics and lactation parameters were also investigated. For the single regressions, the average MU concentration had a positive relationship (R2 = 0.42) with the difference between degradable proteins and fermentable energy (OEB) in the rumen, while the combination of crude protein (CP), net energy (VEM) and week of lactation (WL) more accurately explains the MU variation. The regression of MU prediction obtained with the data file of 14 farms was as follows: MU (mg·dL-1) = 2.56 + 0.130 CP (g·d -1) - 0.00154 VEM (g·d-1) + 0.407 WL (weeks) (R2 = 0.52; s = 6.933; n = 250). This model was significant (P < 0.05) for eleven herds out of fourteen. The results of this study suggest that MU content depends essentially on the protein/energy balance of the diet but that many other factors can influence ureogenesis.