Firm udder in periparturient ewes with lymphocytic accumulations, retrovirus infection, and milk unavailable at the teat.

A condition of firm udders in periparturient ewes, with little or no milk available at the teat, was associated with negative bacterial cultures of mammary tissue, isolation of ovine progressive pneumonia virus from mammary tissue, lymphocytic accumulations in mammary tissue, especially around ducts, and antibody to ovine progressive pneumonia virus in sera. Milk was present in the glands, but was not adequately transported through the duct system. The cull rate of ewes with this condition was reported by producers and veterinarians to be less than 5% in flocks where the condition was recognized, but approximately 10% of ewes were apparently affected in at least 1 flock.