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

Abstract. Title of the paper: The impact of nutrition and non nutrition factors on milk urea concentration. II. The impact of non nutrition factors on milk urea concentration
The object of this study was to determine the impact of non nutrition factors stage of lactation, parity, milk protein 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 but small influence on the milk urea concentration. There was a strong positive relationship between the stage of lactation (day in milk) and milk urea concentration. The regression coefficients for day in milk within the three lactation periods were 0.34, 0.04 and 0.06. This means that the milk urea concentration increases by about 10 mg/1 over 30 days in the first lactation period. The fixed effects for first and second lactation period versus third lactation period were −31.6 and −2.1. Protein yield has a significantly positive influence on milk urea concentration. 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 lactation period if the milk protein yield increased by 0.1 kg/day. The effect of somatic cell count on milk urea was significantly 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 lactation period if the somatic cell count increases by IE5/ml. The relationship between dietary crude protein/energy balance, milk protein yield, stage of lactation, somatic cell count and milk urea concentration can be described by an equation (third paper).