The results of our group’s previous studies on a lipopolysaccharide (LPS)-induced mouse mastitis model and the preventive effects of melatonin on mastitis in mice showed that melatonin administered via gavage significantly suppressed the serum levels of pro-inflammatory factors (TNF-α, interleukin 1β (IL-1β), and IL-6), decreased the levels of malondialdehyde (MDA), and increased the serum levels of anti-inflammatory factors (IL-10 superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT)), which ameliorated the mammary tissue damage caused by LPS [15]. This evidence concerns the gene CAT and mastitis.