BIOLOGY IN HUMAN AFFAIRS 



animal . . . The characteristic differences are definite and 

 well understood. Nevertheless, production costs have 

 increased to such a point that the refinements of the pure- 

 bred in beef conformation and finish subject themselves 

 unfavorably to the law of diminishing returns, since 

 consumers do not pay the price for fancy meats that ordi- 

 narily warrants their production. According to present 

 methods of breeding, stimulation of demand for meats 

 and further improvement of market stock require addi- 

 tional use of expensively produced purebreds. Hence we 

 have arrived at the apparent impasse of requiring better 

 breeding at lower price levels, whereas under practical 

 conditions we can secure better breeding only through 

 higher costs. "^ 



It is becoming clearer and clearer that one of the best 

 ways of using the inherent value of purebred livestock lies 

 in a more extensive use of crossbreeding. The mule is the 

 oldest example of a crossbred animal. This hybrid combina- 

 tion of the horse and the ass has long been appreciated, 

 but, since it is physiologically sterile, it can never be used 

 for breeding purposes. The blue-gray cattle of Scotland are 

 famous. Their distinctive color comes from the genetic 

 composition of black pelt from the Aberdeen- Angus, or 

 Galloway, combined with the white of the Shorthorn. 

 The quick growth and uniformly good meat quality of 

 these mixed breeds are due to the phenomenon of hybrid 

 vigor, commonly associated with the crossing of somewhat 

 unrelated forms. Western sheep in the United States are 

 almost exclusively crossbreds. Swine from Poland-China 

 and Chester White combinations or Duroc-Jersey and York- 

 shire matings are commonly seen in the Corn Belt. Since 

 they can not be used for breeding purposes, there must be 

 good reason for their production. 



^ Record of Proceedings, American Society of Animal Production, Annual Meetings, 

 1925-1926, pp. 42-43. 



[344] 



