• Investigation of the presence and activity of the innate immune component, Complement, in bovine milk

      Maye, Susan; Teagasc Walsh Fellowship Programme (2016-04)
      The occurrence of Complement in human milk indicates the presence of innate immune components of maternal origin and their putative defensive role in the neonatal gut. In order to ascertain the status of Complement in bovine milk, it was necessary to validate the suitability of the Complement-sensitive bacterial sequestration assay used to monitor human milk. The relative bacteriostatic effects, expressed as a differential between the initial and final assay counts following inhibition of the E. coli O111 marker strain were, 6.20 and 6.06 log CFU/ml for raw bovine and human milks, respectively. Lower levels of Complement activity measured in pasteurised and low-fat milks were observed during the course of heat-inactivation studies, while gravity separation of cream over a 24 h period confirmed a greater degree of attachment by Complement to the rising cream layer. The E. coli O111 sequestration assay strain had restricted growth of 7.5 and 8.2 CFU/ml in the higher and lower gravity-separated fractions, respectively. An animal health effect was observed, with Complement appearing to be more active in milk samples from cows with a higher somatic cell counts (SCC). Inducing sub-clinical mastitis in the healthy quarter of a lactating cow confirmed that increased Complement activity effect was local to the affected quarter and not manifested systemically. Complement activity levels varied in the milks of 7 commercially important prominent dairy breeds and crossbreeds surveyed. Both the Norwegian Red and Kerry breed cows stood out as having higher Complement activity (6.25 and 6.92 CFU/ml, respectively); these two breeds are known to have stronger immunity and a better capacity to resist mastitic infection. The findings of this study have implications for both milk production and processing disciplines. In order to retain the antimicrobial efficacy associated with xi Complement in raw bovine milk, milder process treatments than hitherto practised in industry should be adopted.