The concentration of β-carotene and retinol in the blood serum of cows during the transition period

The main goal of our study was to investigate the concentration of β-carotene and retinol in the blood serum of cows during the transition period in summer and winter, and compare their concentrations between healthy and endometritis-affected postpartum cows. The experiment was conducted during both summer and winter periods. The experimental design involved three-time sampling of cow blood during the transition period followed by serum extraction and determination of β-carotene and retinol concentrations. During the late dry period, approximately 15–10 days before calving, all animals exhibited a deficient state of β-carotene with its concentration in blood serum being below 0,40 mg/dL. In postpartum cows, this deficiency became more pronounced. By the end of the transition period, the deficient state of β-carotene persisted in 50,00% of cows in the summer but only in 5,00% of cows in the winter. The concentration of retinol in blood serum during the late dry period remained within the reference range. However, it decreased at the beginning of lactation, with a retinol-deficiency observed in 100,00% of cows in the summer compared to just 5,00% in the winter. By the end of the transition period, the retinol concentration returned to the reference interval. In the summer, the concentration of β-carotene in the blood serum of endometritis-affected postpartum cows was 45,00% lower (p ≤ 0,001) than that of healthy cows, while no difference in retinol concentration was found between sick and healthy cows.