mRNA expression of immune factors and milk proteins in mammary tissue and milk cells and their concentration in milk during subclinical mastitis

Mastitis causes changes of milk protein composition and synthesis of various immune factors. We have investigated if changes take place during subclinical mastitis with somatic cell counts (SCC) between 150,000 and 300,000 cells/ml. The experiment included 8 control animals with a SCC < 150,000 cells/ml (C) and 5 cows with partially elevated quarter SCC showing at least 1 quarter with SCC > 150,000 and ≤300,000 cells/ml (H) and 1 quarter with < 150,000 cells/ml (L).The milk from 1 quarter of control cows and from 2 quarters of cows with partially elevated SCC was collected at one milking. At slaughter mammary tissue of the respective quarters was sampled. mRNA expression of κ-CN was reduced in H compared to L quarter whereas mRNA expression of all other investigated parameters showed no differences between groups in mammary tissue. All immunological factors measured showed elevated mRNA expression in milk cells of H quarters. In H quarters the milk protein content was elevated. Changes occurred despite only mild subclinical mastitis.