UNITED STATES DEPARTMENT OF AGRICULTURE 

 BULLETIN No. 905 



Contribution from the .Bureau of Animal Industry 

 JOHN R. MOHLER, Chief 



Washington, D. C. 



December 8, 1920 



PRINCIPLES OF LIVESTOCK 

 BREEDING 



By 



SEW ALL WRIGHT, Animal Husbandry Division 



CONTENTS 



Evolution of Animal Breeding .... 1 



Reproduction 2 



The Reproductive Cells in Relation to 



Heredity . 11 



Details of Hereditary Transmission . . 15 



The Determination of Sex 23 



Mendelian Heredity in Livestock . . 

 Heredity of Form and Function in Live- 

 stock 



The System of Breeding 



Methods of Selection 



The Value of Purebreds 



30 



34 



42 

 47 

 54 



WASHINGTON 



GOVERNMENT PRINTING OFFICE 



1920 



