Contagious Abortion. 425 



this point depends on the fact that stockowners very commonly 

 dispose of aborting cows, and as the freshly bought cows are 

 usually attacked sooner or later, it is too confidently assumed that 

 the old cows would also have continued to abort had they been 

 retained. Many years ago, however, observant New York dairy- 

 men had noticed that the same cow rarely aborted over three 

 years in succession, and in the great majority of cases not over 

 two. The owner of a large herd, who has had much experience 

 ■with the disease, assures me that the rule has been, that a cow did 

 not abort with him a second time. The continuous abortion in a 

 ■herd was mainly among newly purchased cows and others that 

 had not been previously attacked, including heifers carrying 

 first calf. The same is in a measure true of the European abor- 

 tions. 



Nocard says that after three to five years there is an acquired 

 immunity. Only heifers and the cows that have been recently 

 Thought in, abort. 



Pemberthy, speaking of England, says that in case of repeated 

 abortion in the same cow, the calf is carried longer each succes- 

 sive year until it comes to its full term. 



Sand, in his symposium of the experience of Danish veteri- 

 narians, says it is quite exceptional that a cow should continue 

 to abort, but outbreaks of abortion disappear spontaneously if no 

 new cows are brought in. 



Bang refers to a herd of 200 head of which 83 aborted in their 

 first pregnacy, and of these only 20 aborted in the second, 

 while 7 failed to breed. Counting the latter as having aborted, 

 this amonnts to less than one-third, while over two-thirds of the 

 ■cows that aborted in the first gestation carried the calf to full time. 



Paulsen quotes the case of a herd of 16, 7 of which aborted 

 .after service by a bull in an aborting herd. One of the seven 

 was sold, but the remaining six all went full time in the following 

 year. 



Morck records the case of a herd of 16 cows, the majority of 

 which aborted in the same year. All the aborting cows were 

 sold and fresh ones purchased. Next year the new stock aborted 

 together with some of the cows that had been held over. He 

 continued this course for eight years without any improvement, 

 and then decided to keep the aborting cows as well as the others. 

 In two years the affection disappeared from the herd. 



