Marker selection for udder health alters the cytokine secretion of bovine mammary epithelial cells after bacterial infection

A new strategy to improve udder health is the selection of less susceptible cows using genetic markers for quantitative trait loci (QTL) on chromosome 18, which seems to influence the somatic cell count (SCS) in milk. We established a cell culture model with bovine primary mammary epithelial cells from 28 HolsteinFriesian cows either low (Q) or high (q) susceptible to mastitis and either marker (MAS) or conventionally (CON) selected. The cells were infected for 1, 6, 24 hours (h) with heat inactivated Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) to investigate the secretion of Interleukin-8 (IL-8) as part of the innate immune system in the mammary gland. Material and method Starting from a large pool of heifers, 2 different selection strategies for high and low susceptibility to mastitis as reflected in SCS were applied. The conventional selection strategy relied exclusively on relative EBV for SCS (RZS) estimated in the routine breeding evaluation. In contrast to the conventional strategy, the marker assisted selection strategy primarily relied on marker information regarding paternally inherited marker alleles on chromosome 18. (Griesbeck-Zilch et al. 2009). A human CXCL / IL-8 Elisa Kit (R&D Systems, Minneapolis, USA) was used to evalute the protein concentration of IL-8 in the cell culture supernatants. A recombinant bovine IL-8 (Biomol, Hamburg, Germany) was used as control . The cell supernatants were lyophilised before measurement in order to obtain a higher concentration of IL-8 within the detection limit of the ELISA. Confluent bovine primary mammary epithelial cells