Mastitis, or inflammation of the mammary glands of cattle, is predominantly caused by bacterial pathogens and occasionally by mycotic or algal microbes.

The clear sign of mastitis is inflammation of the udder that turns into a red and hard mass. The swollen mammary gland is hot and mere touching causes pain and discomfort to the animal. Animals do not allow touching of the udder and even kick to prevent milking. If still milked the milk is usually tainted with blood clots and foul smelling brown discharge. Other symptoms are lack of appetite, restricted mobility due to pain, diarrhea, and weight loss.