Mastitis is an infectious disease of sheep. There are two recognized types of mastitis, but the gangrenous type (bluebag) is more severe. With bluebag, gangrene develops rapidly in the udder; ewes become sick, depressed, and feverish. As the infection progresses, the udder, or more commonly, half the udder, becomes hard, red, and swollen. The pain often causes the ewe to limp as she tries to avoid hitting the udder with the rear leg. Affected ewes usually do not let lambs nurse. Within a day or two, the udder generally becomes very hard, gangrene develops, and the udder turns blue. Death occurs in about 25 percent of cases. In ewes that recover, the affected portion of the udder remains nonfunctional. In those that survive, the affected portion of the udder sloughs off.

The nongangrenous type may go unnoticed. The udder becomes hard, swollen, and inflamed, and the milk clots. Abscesses may form in the udder. Milk production is generally reduced, and the udder, or half of udder, becomes nonfunctional. Survival rate is greater than with the gangrenous type of mastitis.

The incidence of mastitis is greater in closely confined flocks than in flocks that are allowed to bed on relatively clean ground. The disease may be spread by the lamb of an infected ewe attempting to nurse other ewes or by milk excreted on the bed ground. Milk and fluids should never be "milked-out"? of the teats in an area where other ewes may contact with the fluids. Separate affected ewes from the main flock and treat with antibiotics as recommended by a veterinarian. Examine the udders of all replacement ewes annually before breeding, and cull any ewes with hard udders.