A Review of milking machine-induced teat-end lesions and susceptibility to mastitis

Abstract

Milking machine-induced teat lesions are commonly thought to be related to increased susceptibility to new intramammary infections. Many of the mechanisms of dimensional and physiological changes in the teat during milking, such as congestion and oedema, are quite well understood. Loss of keratin from the teat canal during milking is believed to lead to increased susceptibility to penetration and colonization by bacteria, but this effect is counterbalanced by the apparent protective effect of the proliferative response to mechanical stress on the teat. This leads to increased regeneration of keratin in the teat canal and hyperkeratosis of the teat-end. Severe teat-end lesions clearly increase susceptibility to new intramammary infections, while some degree of mild hyperkeratosis exerts a protective effect. There is conflicting evidence as to whether moderate hyperkeratosis of the teat-end affects susceptibility to new mastitis infections. Machine-induced teat-end changes may increase susceptibility to mastitis in the presence of other management failures, such as poor milking hygiene.