CHANGES IN EGG PRODUCTION. 123 



Fall production includes October, overlapping into the following months 

 :and thus the next calendar year. It is the season of completion of the 

 «,nnual cycle on the part of most individuals. There is a considerable 

 tendency for the best layers to keep producing, and, as their numbers 

 have increased, it has been reflected in somewhat higher average produc- 

 tion during this period. 



Changes in Variability. 

 As sho'rni by both the standard de"\aation and the coefficient of varia- 

 tion^ (Table III), and by the several frequency polygons (Figs. 7, 11 

 and 15) for ^^■inter egg production, annual production and age at first 

 egg, there has been no especially significant lessening of variability as a 

 result of selection. Selection has merely moved the frequency polygon 

 to one side without changing its general character. 



Influence of Changes in Sanitary Methods. 



The work was commenced on the basis of the best poultry practices 

 available, but the sanitary measures proved wholly inadequate, and suit- 

 able methods had to be developed. There are, however, sufficient checks, 

 indicated especially in Fig. 5, which show, with the exceptions noted in 

 ■the next paragraph, that fundamentally the changes in production are 

 ■due to breeding. 



The low mean production of 1912-13 is due in part to late hatching. 

 Other factors can only be guessed at. The low production of 1914-15 

 is probably due to improper methods of brooding plus disease and poor 

 lielp. 



Recommendations. 



It is difficult, at present, to lay down a series of recommendations that 

 ■can be followed by breeders, with a guarantee that they will work in 

 every case. The following recommendations, based on experience, are 

 intended only for the man who is prepared to go to the necessary expense, 

 time and trouble. 



A. Prerequisites. 



1. Proper management, including housing, feed, sanitation. 



2. Maintenance of -vngor. It is true, hens of poor vigor are sometimes good 



layers, but good vigor as a rule is essential. 



3. (a) Careful trapnest egg records. 

 (6) Careful pedigree records. 



4. A good understanding of both desirable and undesirable egg production 



characteristics in the flock to be improved. 



5. Families of at least seven pullets. 



6. Pullets hatched between March 25 and May 15. 



> The ooefiBcient of variation, if calculated according to the usual formula C. V.= rr XlOO, is 



M 

 a poor index of the real variability, since the range of the polygon does not begin at zero. It is 



•obvious that the formula C. V. = . .... X 100, where X is the lower end of the range, is a better 



index of variability. This is the formula used for age at first egg and for annual production in 



Table III. 



