STOCK BREEDING IXDUSTRY. \y 



or Studies pedigrees, or buys stock to add to his herd or flock, 

 or sells stock from it. Lacking such a definite ideal the breeder 

 is worse oft' than the mariner without a compass, because he not 

 only lacks a means of guidance but also he has no notion of 

 what port he would like to arrive at if he could. 



If he is to be successful the breeder ,must not only have 

 an ideal but must also stick to it, and not change it every 

 time he makes a mating. This implies that the breeding must 

 fall within definite and rather narrow blood lines. It may 

 fairly be said that some degree of narrow breeding (line 

 breeding or inbreeding) is an essential for the highest success 

 in breeding.'" 



This may seem a radical statement, but a careful study of 

 the history of the best improved strains of live stock of all 

 sorts leaves no room for doubt that the attainment of the 

 highest degree of excellence has always been associated with the 

 practice of a very considerable amount of inbreeding, of rather 

 close degree. It is a curious paradox of animal husbandry in 

 general that while, as a matter of fact, every successful breeder 

 of high grade stock practices inbreeding to a greater or lesser 

 extent, a great many of these men are violent, even fanatical, 

 opponents to inbreeding in theory. Most of them will deny 

 stoutly that they ever practice inbreeding. They contend that 

 they practice "line breeding," but never, never "inbreeding." 



The distinction here is obviously verbal and not biological, 

 being in its essentials precisely similar to that betw^een Tweedle- 

 dum and Tweedledee. What is called "line breeding" is simplv 

 a less intense form of narrow breeding than that which is called 

 "inbreeding." The essential and important biological point is 

 that what is actually done is to purify the stock in respect to 

 all characters to as great degree as possible. What the suc- 

 cessful breeder aims to do is to get his stock into such condi- 

 tion that he has only one kind of "blood" in it. Expressed 

 more precisely, though unfortunately more technicallv, it may 

 be said that the breeder endeavors to get his stock hornozvgous 



10 'p, 



The following discussion of iiarrnw breeding is based upon, that 

 contained in a paper entitled "The Biology of Poultry Keeping" by R. 

 Pearl, published as Bulletin 214 of the Maine Agricultural Experiment 

 Station, 19 13. 



