What clinical sign is most consistent with mastitis in a dairy cow?

Mastitis in dairy cows is primarily characterized by inflammation of the mammary gland, which often leads to noticeable changes in the milk produced. One of the clinical signs that best reflects mastitis is the presence of abnormal milk. In cases of mastitis, milk may appear watery or may have a change in color, consistency, or odor due to the presence of pathogens and inflammation. The presence of watery milk suggests a disruption in the normal functioning of the udder due to infection or injury, making it a reliable indicator of mastitis.

Fever is a common response to infection in many conditions, including mastitis, but it is not specific to this condition. Coughing is typically associated with respiratory issues rather than mastitis, and weight loss may occur in chronic conditions but is not a direct symptom of mastitis itself. Thus, the most characteristic sign reflecting the impact of mastitis on milk quality is the production of watery milk, indicating the presence of inflammation and possible infection in the mammary glands.