Changes in the milk, such as flakes, clots, and a watery appearance are the most obvious abnormalities. Heat, swelling, and udder sensitivity are slight or absent. Acute mastitis is a condition characterized by sudden onset, redness, swelling, hardness, pain, grossly abnormal milk, and reduced milk yield. Systemic symptoms may also be present and include fever, loss of appetite, reduced rumen function, rapid pulse, dehydration, weakness, and depression. When the disease onset is very rapid and the signs are very severe, the disease is termed peracute mastitis.
Chronic mastitis is an udder infection that is of long duration.
Nonbacterial mastitis is a mammary inflammation that occurs when microorganisms cannot be isolated from milk samples. Such cases may be either clinical or subclinical.