Release of hydrogen peroxide by phagocytes from bovine colostrum in the peripartum period

Abstract

Changes in the composition of colostrum in the peripartum period focused on the neonate’s immunity can minimize the response of the mammary gland before natural exposure to mastitis pathogens. This research evaluated the oxidative activity of mononuclear and polymorphonuclear phagocytes of bovine colostrum. Bacteriologically negative (n = 171) bovine colostrum samples of first and second milking postpartum were evaluated. The oxidative activity was assessed by the production of hydrogen peroxide (H2O2) released either spontaneously or upon stimulation by enterotoxigenic Escherichia coli (ETEC). For this, three treatments were used: control (C) – only cells; non-opsonized (NO) - cells and ETEC non-opsonized; and opsonized (O) – cells and ETEC opsonized. Median values of concentrations (nmol/106) of H2O2 produced by cells obtained from the first and second milking treatments C, NO and O were 149.1 and 39.9 (P = 0.0007); 125.5 and 49.1 (P = 0.0007); 102.4 and 54.4 (P = 0.008), respectively. No differences were observed between the treatments at each milking. The amount of H2O2 produced at first milking exceeded the values found thereafter. Furthermore, the presence of bacteria did not determine the increased amount of H2O2 released by phagocytes. Thus, we concluded that the mammary gland’s events during the peripartum period have an effect on the proportion and activity of phagocytes, which can cause injuries to the breast parenchyma by the large amount of free radicals produced. The high frequency of bovine mastitis during this period indicates the need for studies of the immunity of the mammary gland and research of susceptibility factors for bacterial infections.