Selected immune traits included serum levels of the pro-inflammatory cytokine TNFα, the expression of which has been associated with disease susceptibility and inflammatory conditions [14], the acute phase protein haptoglobin which is involved in a number of inflammatory conditions of cattle [15], [16] and has been previously associated with breed specific disease resistance in cattle [10], and natural antibodies (NAb) which are thought to be an important antibody component of the innate immune response and appear to be related to frequency of mastitis [9]. Here, TNF is linked to mastitis.