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[Course of the energy balance in the early lactation of Holstein-Friesian cows calculated according to 3 different models].

OBJECTIVE
The aim of this study was to compare the results of the energy balance of dairy cows calculated with 3 different formulas. The course of the energy balance up to the 100th lactation day in Holstein-Friesian dairy cows from a herd with a mean 305-day milk yield of 11 761 kg was to be described.


MATERIALS AND METHODS
Data from a total of 193 dairy cows were available within 2 study periods. Body weight measurements were taken at fixed time points. The feed intake was determined by means of transponder-supported feeding troughs. Milk data was obtained from the corresponding milking recordings. Energy balance was determined by calculation according to the society for nutritional physiology (GfE), Jans and Kessler and National Research Council (NRC) modified according to Collard.


RESULTS
The 3 models yielded very similar results. The calculation modified by Collard, however, generally led to lower values. Minimum values for energy balance were calculated in the colostrum phase. The transition from the negative to the positive energy balance occurred in the mean 53 days postpartum.


CONCLUSION AND CLINICAL RELEVANCE
All 3 calculation methods were equally suitable to assess energy balance of dairy cows conveying similar results. Over 50 % of the examined cows reach a positive energy balance before the 60th day of lactation. According to the literature, the course of the energy balance with a low point around the 60th day postpartum is not to be assumed in principle for each herd. Strategies to improve negative energy balance with regard to time point, extent, and duration in the early lactation must be developed individually for each herd and still require research.