CHAPTER V 

 FERTILITY 



THE larger number of the breeders of domestic animals 

 are engaged merely in the multiplication of animals. 

 They are not primarily striving for the improvement of 

 the species. To all these, the ability of an animal to 

 produce young in abundance is of fundamental impor- 

 tance. To the relatively small class of breeders who are 

 successful in really improving the desirable characteristics 

 of existing breeds, the quality of fertility is likewise of 

 primary importance. When the breeder has succeeded 

 in developing a highly improved strain, it becomes im- 

 portant to secure as many offspring possessing the new 

 and desirable qualities as possible. 



Fertility may be defined as the ability of an animal 

 to produce young in abundance. This quality depends 

 upon the number of young born at one time, the fre- 

 quency of the recurrence of the oestrum, the duration of 

 the period of gestation, and the length of the period of 

 life during which reproduction occurs. All of the above 

 conditions are affected by many circumstances, some 

 external, others internal and inherent in the individual 

 and the species. Many of the circumstances influencing 

 fertility can be directly or indirectly controlled by man, 

 others are beyond his control. 



82. The number of young at a birth. There is very 

 great variation among animals in respect to the number 



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