chaptp:r XV. 



POULTllY DISEASES AND PAIIASITES. 



Maintenance of Health. — Tlie (■onser\'ati()ii of vh^ur and 

 niaiiitenance (if health are fuiidaniental proljleins of poukry 

 production. In tlie last aiial\sis these constitute but a 

 single problem, for great vigor is only an alinndant liealth. 

 The preceding chapters ha\e been gi\'en nj), for the most 

 part, to discussing mcthoils of maintaining liealth, under 

 such divisions as breeding, feeding, and housing. 



In proceeding to a biief and practical discussion of the 

 more common i)oulti'y diseases, it cannot be too greatly 

 emphasized that constructi\'e breeding, with rational feeding 

 and management, is the fii\-,t and principal line of defence 

 against disease. This corresponds in a general way to the 

 construction and maintenance of a. firei)roof l)uilding. Elock 

 treatment to ])revent the si)read of disease that has somehow 

 gained entrance to the fl<jck, corresponds to the efforts of 

 the firemen to save other buildings in the block, for even 

 "fire proof" buildings sometimes burn. I<]ndea\'oring to 

 cure a diseased individual corresjxinds to the efforts to save 

 a badly damaged building from complete destruction, with 

 this very important difference, that while fire in a building 

 may be entirely put out and the damage completely repaired, 

 a bird sick with contagious disease is seldom so completely 

 cured that it does not constitute a source of danger to its 

 flock mates, or so Cjuickly cured that it is capable of complete 

 self repair. A sick fowl may usually be considered as 

 permanently damaged for pi'odnctive purposes. Comparing 

 the small value of an individual fowl with the serious menace 

 to the entire flock of a l)acillus-carrying, cured bird, it is 

 questionable whether it is ever advisable to attempt the 

 cure of birds infected with a contagious disease. 



(503) 



