Changes in the bioactive protein concentrations in the bovine colostrum of Jersey and Polish Holstein–Friesian cows

Abstract

The aim of this study was to determine changes in the bioactive protein concentrations in the bovine colostrum of Jersey and Polish Holstein-Friesian (PHF) cows. Double colostrum samples were collected from 16 Jersey and PHF cows, during 8 successive milking runs after calving. A total of 256 colostrum samples were analyzed to determine the pH, density, percentage share, and content of selected bioactive proteins, including the percentage share of casein fractions (\alpha_s-, \beta-, \gamma-, and \kappa-) in the total casein, and the concentrations of \alpha-lactalbumin (\alpha-LA), \beta-lactoglobulin (\beta-LG), lactoferrin (LF), interleukin-1\beta, interleukin-6, and tumor necrosis factor-alpha. The concentrations of the studied bioactive proteins in bovine colostrum decreased over time after calving, along with changes in the proximate composition of the colostrum. Differences were also noted in the proportions of casein fractions in the colostrum samples collected after successive milking runs: the share of \alpha_s-casein increased, the share of \beta-casein remained stable, and the share of \kappa-casein decreased. The first milking colostrum was characterized by different protein concentrations. The rate of changes in the protein content of the colostrum in subsequent milkings was affected by the breed. In the Jersey cows, a higher percentage share of \kappa-casein and higher levels of \alpha-LA, \beta-LG, and LF in the first-milking colostrum were accompanied by a rapid decrease in their concentrations in subsequent milkings, which points to a correlation between the protein content of the colostrum and the rate of changes in the protein concentrations at subsequent milkings, thus indicating that colostrum is the best source of functional proteins.