Because dairy cows are milked so excessively, NZ dairy cows have increased risks of teat diseases like mastitis. Symptoms of mastitis include include hot, swollen, acutely painful udders, fever, and loss of appetite. When a cow has mastitis her udder may become so inflamed that it is as hard as a stone, and blood bubbles into her milk, which becomes clotted and watery. Severe cases of mastitis can kill a cow in less then 24 hours. Modern dairy cows have been bred for milk production to the point where the teats of their enlarged udders dangle close to the ground, and become muddy and infected.