It is called non-puerperal mastitis.

Mastitis in men is a rare condition but it happens. This is an inflammation of the breast tissue and in men it is referred to as non-puerperal mastitis.

Puerperal fever (from the Latin puer, child), also called childbed fever, can develop into puerperal sepsis, which is a serious form of septicaemia contracted by a woman during or shortly after childbirth, miscarriage or abortion. If untreated, it is life-threatening. The most common infection causing puerperal fever is genital tract sepsis. Other types of infection that can lead to sepsis after childbirth include urinary tract infection, breast infection (mastitis) and respiratory tract infection (more common after anaesthesia due to lesions in the windpipe). Puerperal fever is now rare in the West due to improved hygiene during delivery, and deaths have been reduced by antibiotics.

Antibiotic therapy is the backbone of puerperal infection treatment.

it depends on the type of Mastitis if it is the worst kind toxic mastitis then yes but there are many other types of Mastitis that are not deadly there are also many types of treatments that you could get to help a cow get over its Mastitis