Clinically, it is impossible to distinguish all the variations that may occur, because the constituent tissues are all injured, and the disease is of a mixed type, with very numerous variations.
Symptoms. When chronic mammitis follows the acute form its onset is only indicated by gradual diminution in the signs of acute inflammation. The appetite is regained, and all the important vital functions are properly performed.
Nevertheless, it is possible to distinguish two different clinical forms. In one, the secretion of milk is almost entirely suspended, the udder becomes atrophied, shrivelled and sclerotic; the hardening gradually continues, and the patients, being useless as milch cows, can only be fattened for slaughter. The induration may be partial, nodular, or diffused.
In the other form the udder is large, but the milk is replaced by a purulent secretion which permeates the acini and galactophorous canals. Although they eat well, the patients remain thin, and are with difficulty fattened for slaughter.
The suppuration may be diffuse or local. In rarer cases it is localised in the form of “cold abscess.”
Treatment. No treatment can perfectly restore the udder after chronic mammitis with sclerosis and atrophy.
In the suppurating forms of chronic mammitis the morbid secretion may be checked by internal irrigation of the udder and antiseptic injections, but, as this treatment necessitates careful and continued attention, it is usually out of the question.
If only one quarter is diseased the animal may be kept for milking purposes, but where two or three quarters are attacked it should be prepared for the butcher.
In cows suffering from chronic purulent mammitis of all four quarters, Kroon suggests removing the teats in order to facilitate fattening. The teats are removed with the bistouri or scissors, by which means a large opening into the galactophorous sinus is produced, through which the purulent secretion escapes freely and continuously; the retention of pus and intoxication in consequence of resorption are prevented and the animal can be fattened, which would be difficult without the operation.