The study was conducted in herd of primiparous Polish Holstei-Fresian dairy cows. Milk samples were collected during test milkings. The following parameters of milk samples were examined: total bacteria count, somatic cell count, milk urea nitrogen, total casein content, rennet coagulation time. Individual protein fractions were also determined. Changes in the characteristics of milk depending on the stage of lactation were analyzed. Conducted study has shown that the level of κ-casein in the XIII month of lactation decreases in comparison to the level of the III, IV, V, VII and VIII month of milking. No significant effect of lactation stage on the α-casein and α-lactoalbumin content in milk was observed. There was no statistically significant relationship between the day of milking, and the total casein content. The lowest somatic cell count was reported in milk from cows in VI, X and XII month of lactation (<180 000 · ml^-1).

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