A secondary goal of this experiment was to determine the dynamics of β-defensin gene expression in response to LPS challenge. Expression of DEFB3, DEFB4, DEFB5, and DEFB10 has been documented in infected (Kościuczuk et al., 2014) and healthy (Tetens et al., 2010) bovine mammary glands. Lipopolysaccharide treatment induced expression of several β-defensins in mammary epithelial cell and neutrophil cultures (Merriman et al., 2015), but the dynamics and factors controlling their expression in the mammary gland were not known.We observed that LPS stimulated DEFB3, DEFB4, DEFB7, and DEFB10 in somatic cells within several hours after challenge. In agreement with in vitro experiments, the response of the β-defensins to intramammary LPS also was more dramatic in neutrophils compared with macrophages (Merriman et al., 2015).Although not shown, similar results were observed for expression of the gene for lingual antimicrobial peptide, another member of the bovine chromosome 27 β-defensin gene family, which also was induced by intramammary LPS challenge in a previous experiment (Isobe et al., 2009). Expression of DEFB5, on the other hand, decreased at 4 h after LPS challenge, which is similar to the response of monocytes but contrary to the response of mammary epithelial cells and neutrophil cultures (Merriman et al., 2015). Of the β-defensin genes, the response of DEFB10 was most dramatic, increasing more than 200-fold compared with baseline expression.The DEFB10 peptide also was the most abundant β-defensin peptide in milk fat globules from glands infected with Staphylococcus aureus (Reinhardt et al., 2013), highlighting the potential significance in defense against bacterial infection of the mammary gland.