Antioxidant potential of milk obtained from Holstein-Friesian cows with regard to the subsequent lactations and stage of lactation

The aim of the research was to assess the content of components showing antioxidant activity in the milk of Holstein-Friesian cows and changes in the total antioxidant status during subsequent lactations and their stages. The material for analysis consisted of milk collected from 90 cows (30 for each analysed lactation number: I - primaparous; II - multiparous in second lactation; III - multiparous in third lactation) during three periods: 1 - up to 100 days of lactation, 2 - 101-200 days of lactation, and 3 - 201-305 days of lactation. The basic chemical composition, casein content, somatic cell counts, selected whey proteins and fat-soluble vitamins were determined in the milk. The total antioxidant status (TAS) of milk was also measured. With the subsequent lactation, the content of components with antioxidant properties, i.e. vitamins A and E, and albumins (α-lactalbumin and β-lactoglobulin), decreased significantly (p≤0.01). Simultaneously, a decrease in the level of TAS in milk was noted. The lactation phase had a minor effect on the antioxidant potential of milk. The obtained high correlation coefficients between the value of the TAS and the content of vitamins A, E and β-lactoglobulin indicate that the content of these compounds largely determines the antioxidant potential of milk. On the other hand, the obtained negative correlations between the level of antioxidant potential and the daily milk yield (r = -0.347, p≤0.05) suggest that the high productivity of cows negatively affects the antioxidant value of milk.