PREFACE 



THE material in this book has been drawn from three 

 sources : from practical experience ; experimental studies, 

 particularly of feeding questions; and the results of re- 

 search in the field of chemistry and biology. The dis- 

 cussion on general care and herd management is chiefly a 

 statement of the methods that have proved most suc- 

 cessful in practical experience. That part of the book 

 dealing with questions of feeding is largely the result of 

 a careful analysis and summary of the mass of experi- 

 mental data available on this subject. The discussion 

 of breeding problems has for its foundation the approved 

 methods of the constructive breeders and the important 

 facts recently discovered in the field of genetics which 

 have a bearing on the practical questions related to 

 animal breeding. 



In its preparation the author has sought and received' 

 many facts and suggestions from hog men, commission 

 salesmen, experiment station workers, packing-house 

 officials, and animal husbandry teachers, without which 

 the book in its present form would not have been possible. 

 For the help thus received he wishes to express grateful 

 acknowledgment. For much of the data presented in 

 chapter five he is indebted to W. J. Carmichael formerly 

 of Illinois University and now secretary of the National 

 Swine Growers Association. To the members of the 

 Animal Husbandry staff of Purdue University he wishes 

 to express his appreciation of their kindly criticisms, 

 encouragement, and help. 



W. W. SMITH 



PURDUE UNIVERSITY, 

 January 1, 1920 



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