No abstract

Most cows experience a period of nutrient deficit during the periparturient period. Body condition scoring (BCS) is widely used on farms to assess body nutrient reserves and mobilization. The aims of this study were to: (i) determine the association of BCS with ultrasound measurements of backfat (BFT) and longissimus dorsi muscle thickness (LDT) during the periparturient period of Holstein cows from different herds, accounting for potential sources of variation, such as herd, parity and period relative to calving and (ii) establish reference intervals (RIs) for BFT and LDT per BCS estimate. Two-hundred and fifty-two cows from six commercial farms were used. Body condition scores, BFT and LDT were assessed at seven time-points during the periparturient period. Assessments of BCS estimates as predictors of BFT and LDT and the contribution of BFT and LDT to BCS estimates were performed with the use of linear mixed models. Reference intervals for BFT and LDT per BCS estimate were established with the Reference Value Advisor. One unit of BCS change was associated with 8.2 mm of BFT and 10.9 mm of LDT pre- and postpartum. Range of BFT and LDT in established RIs per BCS was wide with significant overlap. Both subcutaneous fat and, to a lesser degree, skeletal muscle reserves contribute to BCS estimation. Repeated BCS estimations credibly predict energy balance status in periparturient dairy cows. The metabolic state of muscle tissue should be assessed by repeated ultrasound measurements.

No abstract

ABSTRACT. Milk urea nitrogen (MUN) is an important tool in dairy cow nutrition, as it reflects the amount of nitrogen in the diet which is not used for production. The objective of this study was to evaluate MUN values in Greek dairy herds, for the first time, and to investigate the source of its possible variation. For this purpose, a dataset of 23,266 milk records from 24 Holstein herds in the region of Thessaly (Greece) was used. Descriptive statistics, analysis of variance and a multiple regression model were used for statistical analysis. Significant differences were observed among farms (P<0.05). Mean MUN concentration was 15.54 mg/dL. More than 90% of the measurements were above the upper limit of reference herd target-values. In contrast with previous observations, lower MUN values (P<0.05) were observed during the summer and autumn. A positive relationship between milk yield and MUN was observed, but only up to MUN values of 16 mg/dL. Milk fat content and fat/protein ratio were negatively related to MUN, while cows with higher protein content had lower MUN values (P<0.05). Most milk traits and sampling month explained only 25.8% of the variation in

No abstract