The aim of this study was to determine selenium concentration in the blood serum of dairy cows and to establish its influence on the level of production and reproduction traits. The study was performed on the farm located in Western Pomerania and involved 140 cows, which were selected using the analogue method on the basis of their physiological state, lactation number, milk yield, age and genotype. The following indices were analyzed in individual groups: milk yield (kg), milk fat yield (kg), milk fat content (%), milk protein yield (kg), milk protein content (%). Selenium concentration in the blood serum was determined with the spectrofluorometric method. The obtained results showed that 23.6% cows had selenium deficiency, 39.3% had threshold concentration and 37.1% had physiological concentration. The mean milk fat and protein contents were the highest in animals with the threshold concentration of selenium and differed statistically (P≤0.01) from those of the group with the deficiency or physiological concentration of this element. The study revealed that the problem of selenium deficiency is still present in some dairy cattle herds in Western Pomerania.

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