EN
The study group consisted of 60 Holstein-Friesian cattle from farms situated in the central part of the Lublin region in Poland. The cows were kept in a tethered system and fed a TMR or a PMR. It was found that the animals had reduced concentrations of serum macroelements in the puerperal period. Therefore, the amount of a prophylactic mineral additive was increased by 50%. The study was conducted 6-8 weeks after parturition and directly before the dry period. The aim was to determine the influence of the increased doses of the mineral additive on the contents of calcium, phosphorus, and magnesium in serum, as well on the functions of parenchymal organs, to assess the health status of the herd. The results showed that an increased amount of supplements may lead to elevated values of the above macroelements (even higher than physiological standards) in many cows in the herd, which can be particularly dangerous in the absence of regular monitoring of blood biochemical parameters. Moreover, lower conception rates, problems with the musculoskeletal system, and further disorders in the puerperal period have also been reported.