100 THE BREEDING OF ANIMALS 



in the best condition for the successful exercise of the 

 breeding function. A rapidly improving condition due 

 to nutritious food supplied in generous quantities is 

 distinctly favorable, provided the animal is not already 

 too fat. 



E. Davenport has held that, " excessive food supply 

 leads to infertility among both plants and animals." 

 This is true of long-continued and excessive feeding, but 

 a rapidly improving condition of the animal in thin condi- 

 tion is distinctly favorable to the highest fertility. It is 

 a mistaken idea that starvation or a very limited diet 

 is a favorable environment for the successful activity of 

 the generative system. Such treatment is only favorable 

 in the case of over-fat animals and is oftener the first 

 and a very essential step in securing offspring from animals 

 that through a long period of overfeeding become tem- 

 porarily barren. 



98. Other factors affecting fertility. A sudden change 

 of conditions surrounding the animal, such for example 

 as the exportation of an animal from Europe to the United 

 States, will often temporarily interfere with the normal 

 activities of the reproductive system and the animal 

 may be barren for a time. When the animal has become 

 thoroughly accustomed to the changed conditions, its 

 breeding powers return and thereafter may function 

 normally. Changed conditions may also result in in- 

 creased fertility. As shown elsewhere, breeding animals 

 in thin condition and existing upon a sparse ration or upon 

 a dry dietary, become markedly more fertile when changed 

 to richer pastures. 



Some individuals are infertile when mated with cer- 

 tain other individuals, but may be fully fertile with others. 

 A mare may be sterile when bred to a stallion, but fertile 



