Fütterungs- und nicht fütterungsbedingte Einflüsse auf den Milchhamstoffgehalt von Milchkühen ndash; 2. Mitteilung: Nicht fütterungsbedingte Einflussfaktoren auf den Milchhamstoffgehalt von Milchkühen

摘要

Title of the paper: The object of this study was to determine the impact of non nutrition factors stage of lactation, parity, milkprotein yield, somatic cell count, season and herd on milk urea concentration. For parity one to fife 239, 242,238, 235 and 237 mg urea/l milk was calculated using least-squares-means. Parity has a Statistical significant butsmall influence on the milk urea concentration. There was a strong positive relationship between the stage oflactation (day in milk) and milk urea concentration. The regression coefficients for day in milk within the threelactation periods were 0.34, 0.04 and 0.06. This means that the milk urea concentration increases by about 10mg/1 over 30 days in the first lactation period. The fixed effects for first and second lactation period versus thirdlactation period were −31.6 and −2.1. Protein yield has a significantly positive influence on milk ureaconcentration. The regression coefficients for milk protein yield within the three lactation periods were 42.5,43.2 and 31.2. This means that the milk urea concentration would increase by about 4 mg/l in first lactationperiod if the milk protein yield increased by 0.1 kg/day. The effect of somatic cell count on milk urea wassignificantly negative. The regression coefficients for somatic cell count within the three lactation period were −0.017, −0.019 and −0.015. This means that the milk urea concentration will decrease by 1.7 mg/l in first lactationperiod if the somatic cell count increases by IE5/ml. The relationship between dietary crude protein/energybalance, milk protein yield, stage of lactation, somatic cell count and milk urea concentration can be describedby an equation (third paper).