Inline changes in lactate dehydrogenase, milk concentration according to the stage and number of lactation periods, including the status of reproduction and milk yield in dairy cows.

The aim of the present study was to investigate inline lactate dehydrogenase (LDH) dynamic changes based on different cow factors - different number and stages of lactation, milk yield, and the status of reproduction in clinically healthy dairy cows. In the Herd Navigator system, LDH activity levels (μmol/min per litre) were measured using dry-stick technology. A total of 378 cows were selected. According to their reproductive status, the cows were classified as belonging to the following groups: Fresh (1 - 44 days after calving); Open (45 - 65 days after calving); Inseminated (1 - 35 days after insemination); Pregnant (35 - 60 days after insemination and pregnant). According to their productivity, the cows were classified into the following groups: ⟨15 kg/day, 15 - 25 kg/day, 25 - 35 kg/day and >35 kg/day. The cows were milked with a DeLaval milking robot (DeLaval Inc. Tumba Sweden) in combination with a Herd Navigator analyser (Lattec I/S. Hillerød Denmark). In conclusion inline dynamic changes in the milk LDH concentration may increase together with the rise in the lactation period frequency. The highest LDH level determinated in the group of the fresh cows ranged from 5 to 10 DIM, while the highest LDH concentration level was found in the fresh cow milk. Thus, there was a positive relationship between the milk concentration of LDH and the milk yield.