Infectious Abortion of Mares 481 



Infectious abortion in the mare may occur at any stage during 

 pregnancy — an observation which possibly holds true to a great 

 extent for other domestic animals. The abortion is most ire- 

 quently observed, however, after the fetus has acquired con- 

 siderable size, so that it is most usually noticed after the 6th to 

 8th month and even more commonly during the loth and nth 

 months. In some of our observations, however, the abortion 

 had apparently occurred very early, although no positive proof 

 of this was obtainable. In fact it is exceedingly difficult. to 

 obtain proof of abortion during the first few weeks of pregnancy, 

 since the small embryo, with its inconspicuous membranes, may 

 be expelled without attracting any* attention whatever on the 

 part of the owner and does not interfere in the least visible de- 

 gree with the general well-being of the animal. 



In our investigations, there was one well-defined instance 

 where very early abortion seemed to be well proven. An ex- 

 tensive breeding farm had over 100 breeding mares, some of 

 which were imported draft animals and the others highly bred 

 trotting mares. They were unusually well kept, under as favor- 

 able conditions as breeding animals could well be placed. The 

 mares were at pasture upon good blue-grass, which was quite 

 free from herbage having any suspicious character in reference 

 to breeding. The mares were 3'oung and in excellent general 

 health. The stallions were vigorous and well handled and had 

 previously shown themselves to be regular and sure breeders. 

 During one season these mares of both breeds seemed to con- 

 ceive readily upon being bred, and upon being re- tried to the 

 stallion they showed no signs of estruni and were apparently 

 safely in foal. After they had been re-tried one, two or three 

 times successfully, it was found that later they showed estrum 

 and again had to be bred. The condition was very puzzling to 

 the superintendent and no explanation was apparent during the 

 spring and early summer. 



Finally, in early autumn, when some of the mares had safely 

 carried their foals for several months, there was occasionally 

 found in the pasture a partially matured fetus. As the season 

 advanced well nigh all of the few mares, which during the breed- 

 ing season had constantly shown signs of being in foal, aborted, 

 and the foal crop was well nigh ruined. Here it would seem that 

 there was good evidence that many of these mares aborted during 

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