114 PRINCIPLES OF STOCK-BREEDING. 



must also be looked upon as taking its share in influ- 

 encing the reproductive functions. When the fall of 

 rain has been small, and the herbage more than usu- 

 ally parched, we find unusual difficulty in getting ordi- 

 nary farm-stock' to breed a dry dietary is very un- 

 favorable for breeding animals, and very much retards 

 successful impregnation. On the other hand, rich, 

 juicy, and succulent vegetation is very generally favor- 

 able to breeding. Apart, therefore, from the direct 

 influence of the food given, it is certain that the con- 

 dition in which it is consumed materially influences 

 the breeding powers." 1 



Mr. Mills, in his " Treatise on Cattle," published 

 in 1776, remarks that " mares which have been brought 

 up in the stable on dry food, and afterward turned to 

 grass, do not breed at first ; some time is required to 

 accustom them to this new aliment." 2 



In the wild species that breed twice a year it has 

 been stated that the time of breeding is determined 

 by the abundance of food ; but this does not appear 

 to be the case with migratory birds, in which the im- 

 pulse to nest-building and migration occur together, 

 at an early period in the spring, before they can ob- 

 tain an abundant supply of food. 



There seems to be a marked relation between the 

 size of animals and their fecundity, which may per- 

 haps be owing, in part at least, to the modifying influ- 

 ence of the nutritive functions. Throughout the en- 

 tire animal kingdom the small species of animals ap- 

 pear to be more prolific than large ones, and, as a rule, 



1 Journal of the Royal Agricultural Society , 1865, p. 269. 



2 Loc. cit., p. 66. 



