Cause: Mastitis is often caused by bacteria like Escherichia coli, Staphylococcus aureus, coagulase-negative staphylococcus, Streptococcus agalactiae, Str. uberis, Str. dysgalactiae, Arganobacterium pyogenes or Corybacterium bovis. It is important to test the infection milk to find out which bacteria is causing the infection, so the correct preventive measures can be taken. E. coli for example comes usually from filty stalls, Str. dysgalactiae is found with injuries and Str. agalactiae infection is always from another cow.
Symptoms: Symptoms vary, but the most common ones are fever, swelling and warmth in the infected part of the udder, abnormal milk, reduced milk yield, loss of appetite and reluctance to give milk due to soreness in the udder.
Treatment: "Common treatment" may be costly and useless. For effective treatment the cause of mastitis must be studied. Str. agalactiae responds well to penicillin, but E. coli may need stronger antibiotics plus supportive treatment, because it often also causes severe diarrhea. C. bovis infections are best treated with teat disinfectants and drying off (stopping her from lactating until the next calving).
Prognosis: After severe mastitis the infected quarter may go dry entirely, or it must be amputated as a treatment. This leaves the cow with only three teats, decreasing its milk yield. Some cows which get mastitis often may need to be slaughtered. An epidemic of mastitis is always a cause to re-evaluate the conditions in and cleanliness of the barn.
Cause: The cow may step on her teats if she cannot lie down or stand up naturally due to slipper floor or other environmental problems. In a cramped barn, cows may step on each other's udders. Adult cows sucking milk from each others, fights and faulty milking machinery may also cause teat damage.
Symptoms: In chronic (long-term) teat injuries the milk channel gets thicker over time and may get clogged. Round, hard growths may be felt in the teat. Milk letting is slow. In acute (sudden) injuries the milk may be bloody, teat shows external damage. A gangrene may develop on to the skin of the udder, and the udder may turn blue.
Treatment: Injured teats must be kept clean. The cause for the damage must be removed, if possible. Deep or long wounds in the teat should always be treated by a vet, so they heal better. Gangrenes can be left to heal on their own, but treating a possible infection and keeping the udder clean are very important. Chronic teat injuries like clogged milk channels can be surgically opened by a vet, but the prognosis is not good.
Prognosis: Prognosis depends a lot on the nature of the injury. Small acute injuries often heal well. Chronic injuries may keep getting worse if the cause isn't quickly removed, and have worse prognosis.