Comparison of ultrasonographic measurement of backfat thickness with combined measurement of backfat-muscle thickness as a measure for body condition assessment of dairy cows The aim of the work was to relate the method of backfat-muscle thickness measurement (BFMT) to the scientifically recognised methods for assessing the body condition of dairy cows. It was to be tested whether BFMT provides reliable, reproducible and meaningful information on the body condition of dairy cows, whether the new method has advantages over the known methods (BCS, live weight, BFT), whether muscle thickness is related to backfat thickness (BFT), whether protein depots are essential for the assessment of body condition and whether there is a correlation between BFMT at calving and milk yield as well as fertility. For this purpose, 3671 measurements were taken in 339 cows at different times before and after calving. Among the subjects were 262 multiparas cows and 77 uniparas. When looking at the data collected, a significant correlation was found between the lactation number and the backfat-muscle thickness. A slight increase in BFMT was seen with increasing lactation number. This should be taken into account when using the measurement method in the herd level survey. The comparison of the BFMT with the scientifically recognised methods of backfat thickness measurement, the body condition score and live mass weighing showed a significant correlation. It could be concluded that the backfat-muscle thickness measurement provides reliable values for condition assessment. When comparing the BFMT with the BCS, the new measurement method is preferable to the BCS due to its objectivity. Backfat-muscle thickness measurement is also preferable to weighing for live mass weighing. The BFMT is subject to fewer influencing factors. When comparing the BFMT with the BFT, a close agreement of the measured values is noticeable. The two examination methods can be considered almost identical. They only differ in the easier finding of the backfat-muscle thickness measurement point and the missing minimum value of the BFMT. By comparing the reference values of the backfat thickness, the following reference values can be recommended for the backfat-muscle thickness: Time: a) Start of the dry period, b) Calving (multiparas), c) Calving (primiparas) Reference value of the BFMT: a) 30-35mm, b) 31-40mm, c) 27-32mm The BFMT showed a clear decrease in early lactation resulting from the mobilisation of fat and protein for energy production. The separate evaluation of the immediate muscle thickness confirms the mobilisation of protein. Due to the identical results of the backfat thickness and backfat-muscle thickness measurements, the documentation of protein mobilisation is not essential for the assessment of body condition. The backfat thickness already provides sufficiently reliable condition values for assessing the dynamics of the energy metabolism of dairy cows. A significant correlation was found between backfat-muscle thickness and 100-day milk yield as well as the fat-protein ratio. There was no correlation with 305-day milk yield. Furthermore, there were no significant relationships between BFMT and the fertility parameters intercalving period and insemination frequency. Due to the close correlation between backfat-muscle thickness and the condition parameters, with special attention to backfat thickness, backfat-muscle thickness measurement can be recommended as a method in herd management for optimising animal health, milk yield and fertility in dairy farms. However, no added value can be recognised in comparison to the statements of the backfat thickness measurement.weiterlesen