Gra7iular Ve^iereal Disease of Cows 1 103 



The prognosis of the disease, based upon European observa- 

 tions and those thus far made in America, is very unfavorable 

 unless vigorous prophylactic and curative measures are insti- 

 tuted. Some believe in spontaneous recovery, and there is much 

 to support this belief. In one stable in Herd 2, there is a number 

 of aged cows, which are apparently sound, breed regularly and 

 promptly, and give birth annually to healthy, vigorous calves. 

 These animals stand side by side with diseased cows year after 

 year, and are served by the same bull, and the diseased and 

 healthy cows are groomed with the same utensils and handled 

 by the same persons without precautions. These facts combine to 

 indicate either that these cows have always possessed immunity 

 or have at one time been diseased, have recovered, and acquired 

 immunity against the malady. 



How long a time is required for such spontaneous recovery is 

 purely speculative. In most of the herds observed, 50 to 80% of 

 the aged cows are now affected, and the history of most of these 

 herds indicates that they have been infected four or more years. 

 If these assumptions are correct, the outlook for early spontane- 

 ous recovery is certainly poor. A pregnant affected cow brought 

 to the college has now been under observation five months, is not 

 exposed to fresh infection, and is well kept ; but the lesions are 

 now as pronounced as they were when first examined. 



Our observations indicate, however, that diseased animals, 

 after a time, acquire a degree of immunity against the effects of 

 the disease. A cow aborts one year, perhaps a second year, and 

 possibly a third, and then proceeds to carry her calf full time, 

 and it is born vigorous and healthy. In an aborting ierd, the 

 body of the herd largely ceases to abort. New cows introduced 

 into the herd very largely abort. Heifers raised in the herd, 

 and probably infected at the first breeding, abort the first calf ; 

 and, if they remain fertile, probably abort the second calf; and, 

 passing this ordeal, may breed regularly. 



The prevalence of sterility is apparently somewhat analogous. 

 If the cow continues to breed for the first few years after she 

 has become diseased, she will probably continue to breed per- 

 manently. Sterility is very common and ruinous in herds where 

 the disease is already present in the virgin heifers, and the basis 

 for the sterility is laid prior to coition. Such sterility defeats 

 the breeder and dairyman wholly. 



