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.

Evaluation of rumination time, subsequent yield, and milk trait changes dependent on the period of lactation and reproductive status of dairy cows.

The aim of this research was to determine rumination time (RT) and the subsequent milk yield, along with trait changes during lactation dependent on the reproductive status of dairy cows. 728 cows were selected for evaluation in regards to 1-150 days of milk production (DIM). According to their period of lactation and reproductive status, the cows were selected for the following groups: Inseminated (1-35 days after insemination, n=182), Open (45-90 days after calving, n=126), Fresh (1-44 days after calving, n=45); Not-pregnant (>35-60 days after inse- mination and not-pregnant, n=55); Pregnant (35-60 days after insemination and pregnant (n=320). The animals were milked with Lely Astronaut® A3 milking robots. The daily milk yield, rumination time, bodyweight, milk composition (fat, protein, lactose, somatic cell count and gynecological status date) were collected from the Lely T4C management program for analysis. We estimated the lowest productivity in the pregnant cows, where the average milk yield was 28.72 kg and the highest productivity in the fresh cow (p⟨0.001)(Table 1). The longest rumina- tion time was determined for the inseminated cows, statistically significantly higher at 9.92% (p⟨0.001) than in the non-pregnant cows, whose rumination time was the shortest. The statisti- cally reliably RT positively correlated with productivity (r=0.384, p⟨0.001) of the cows (from r=0.302 in the second lactation and r=0.471 in the first lactation to r=0.561 in multiparous cows; p0.001). Rumination time, according to groups of cows by milk yield, had a tendency to increase (2.14 times) from 202.0± 87.38 (in cows with a productivity of less than 10 kg milk) to 431.6±33.91 (in cows with a milk yield higher than 50 kg) by the linear regression equation: y = 38.02x + 232, R² = 0.721 (p⟨0.001). The relation between the gynecological status and milk fat-protein ratio of the cows was statistically significant (χ2=2.974, df= 8, p ⟨0.0001). The longest rumination time was determined for the inseminated cows (1 - 35 days after insemination), and the shortest for the not-pregnant cows (>35 - 60 days after insemination and not-pregnant). We can conclude that rumination time, subsequent yield, and milk trait change depends on the period of lactation and reproductive status of a dairy cow.

Sequential cobalt magnetization collapse in ErCo2: beyond the limits of itinerant electron metamagnetism.

The itinerant electron metamagnetism (IEM) is an essential physical concept, describing magnetic properties of rare earth - transition metal (R-TM) intermetallics, demonstrating technologically important giant magnetoresistance and magnetocaloric effects. It considers an appearance of TM magnetization induced by spontaneous magnetization of surrounding R atoms, which provides significant response of the magnetic and transport properties on variation of external parameters (temperature, pressure, magnetic field) due to strong coupling between magnetic sublattices. The RCo2 compounds were generally considered as model systems for understanding of basic properties of IEM intermetallics. However, microscopic nature of magnetic properties still remains unclear. In our experimental and theoretical study of ErCo2 in a wide range of thermodynamic parameters a sequential collapse of cobalt sublattice magnetization in the background of nearly unchanged Er sublattice magnetization was revealed. The uncoupled magnetizations behavior challenges the IEM concept applicability and evidences more complex nature of magnetism in ErCo2 and related RCo2 systems.