Association studies between polymorphic variants of TLR-encoding genes and mastitis in dairy cattle. An overview of the current state of knowledge

Mastitis is an inflammation of the mammary gland which occurs as a defensive reaction to microorganisms that have penetrated the body. The disease generates huge financial and economic losses as treatment of affected cows is expensive but not always effective, which translates into a decrease in the amount of milk that they produce. Due to the huge number of pathogens and their molecular diversity, the immune system has developed various mechanisms to combat them. What raises hopes for improved udder health is marker assisted selection (MAS) or genomic selection. The molecular diversity of microbes allows them to be considered genetic markers, and Toll-like receptors (TLRs) are suitable candidates. TLRs recognize infectious agents and trigger mechanisms to combat them, including by the production of pro-inflammatory cytokines, chemokines and interferons. Due to the role these receptors play in the body, TLR-encoding genes may be associated with bovine mastitis resistance.