il6 maine agricultural experimlnt station. i9io. 



Technical Studies on Poultry Already Published. 



A considerable portion of the more technical scientific work 

 of the department of biology of the Station, which has in 

 charge the work with poultry, is published in current biological 

 journals, not readily accessible to the agricultural public. It 

 is the purpose of the present section of this bulletin to give 

 briefly the essential points brought out in certain of these tech- 

 nical studies which have been published during the past year. 



selection index numbers in poultry breeding.* 



It is an obvious fact that a breeder practically never wishes 

 to improve only one single characteristic of the plant or animal 

 which he is breeding. What is usually desired is to improve 

 -several characteristics at the same time. Thus, with dairy 

 cattle, while the main object in breeding is to increase the 

 amount and quality of the milk, other things such as constitu- 

 tional vigor, breeding capacity and the like cannot be lost sight 

 of in making the selections of breeding stock. Or in corn 

 breeding, to take an illustration from the plant side, while one 

 may be desirous of increasing the protein content of corn, in 

 breeding for it he must always keep in mind the conformation 

 of the ear, size of ear, yield and a whole series of other char- 

 acteristics. 



One of the special objects of the poultry breeding work at 

 the Station is to learn how to fix superior egg production in a 

 strain by breeding. In any poultry breeding, whatever may be 

 the special object of the breeder, a fundamentally desirable 

 thing is reproductive or breeding capacity in the birds. A 

 "200-egg" hen is of very little value as a breeder if she is not 

 able to produce when mated with a good male bird a fair per- 

 centage of chickens which will live. 



It is very generally stated by practical poultrymen that the 

 point on which it is most often decided whether a given com- 

 mercial venture in the poultry business shall succeed or fail is 

 the expense involved in the hatching and rearing of the chick- 

 ens. The female that will produce eggs which will yield a 



*This section is an abstract of a portion of the following paper by R. 

 Pearl and F. M. Surface: "Selection Index Numbers and their Use in 

 Breeding." American Naturalist, Vol. XLIII, No. 511, pp. 385-400, 1909. 



