Dynamic of subcutaneous and abdominal adipose depots during the transition period of German Holstein dairy cows with different body condition and the effects of monensin Adipose tissue depots have an important role in dairy cows as they are usually mobilized after parturition in response to negative energy balance (NEB) a consequence of increased nutrient demand of fetal growth and onset of milk production which cannot be satisfied by feed intake. The most common methods to evaluate fat depots thus the condition of the cows are measurement of body weight and body condition scoring. However these procedures lack the accuracy to predict changes of subcutaneous and internal fat depots. Recently a new method was developed to assess the mass of different fat depots by ultrasonography. This method allowed to assess non invasively mass of subcutaneous and abdominal adipose depots with sufficient accuracy and changes of these depots over time in vivo. Earlier studies used this method to evaluate the adipose tissue mass of different depots the changes in depot masses as well as the effect of feed additives on depots. The results of these studies showed that more fat accumulates in abdominal (AAT) depots and that AAT has greater lipolytic activity compared to subcutaneous (SCAT) depot. The aim of this work was to evaluate the fat depots of dairy cows with higher and lower body condition during the transition period and early lactation. We found that ultrasonography was a suitable tool to determine the depot masses and to follow their changes over time. Our results were similar to those presented in earlier studies. The mass of the adipose depots increased during the dry period and decreased after calving. The SCAT had smaller mass than AAT during the whole trial period as well as that more fat was mobilized from AAT compared to SCAT after calving. This indicates that AAT has a greater role in fat storage and mobilization in dairy cows. Further we found that leaner cows had smaller adipose depots and mobilized less fat after parturition. Additionally we found a lack of correlation between NEB and mobilization of adipose depots during the fresh cow period suggesting NEB is not the only cause of fat mobilization in this period. Mechanisms involved in homeorhetic adaption to lactation such as decoupling of somatotropic axis responsiveness to insulin or β adrenergic stimulation of lipolysis as well as inflammatory stimuli could have affected the usage of fat depots. Our results point to complexity of adipose metabolism and further research could better elucidate the underlying effects. Another part of this study was to examine the effects of monensin (MON) an ionophore on fat depots and mobilization. Earlier studies found that MON decreases the levels of non esterified fatty acids one of the indicators of the level of fat mobilization in dairy cows after calving which might indicate an antilipolytic activity of this compound. We could not prove this hypothesis as MON had no effect on fat depo masses or their change. The lack of MON effect on post calving NEFA levels further strengthened our findings. These results suggest that MON most likely effects the hepatic or post hepatic utilization of NEFA in the period after calving. We examined and compared the daily activity of leaner and fatter dairy cows a possible additional cause for higher NEFA levels in cows with higher body condition. Muscles can use NEFA to cover their energy requirements during the transition period. Authors of a recent publication reported a negative correlation between NEFA levels and walking activity of dairy cows. This might indicate that fatter cows are less active thus using less NEFA during the transition period conversely leading to higher NEFA concentrations. However our results do not support this as there was no difference in daily activity of cows with low and high condition after calving. On the other hand activity is an indicator of animal welfare and comfort. In the dry period the fatter cows had higher number of lying bouts compared to lean cows: This could indicate that cows with higher condition experienced less comfort during lying as a consequence of greater body mass. Taken together the results of this study show that there are significant differences between the subcutaneous and internal adipose depots not just on cow level but between the individual animals too. Additionally it was demonstrated that monensin as well as daily activity did not affect the adipose depots of dairy cows.