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 

 annual 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 shown by both the standard deviation and the coefficient of varia- 

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

 and 15) for winter 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. 



Injhience of Changes iii 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 

 help. 



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 

 eveiy 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 vigor. It is true, hens of poor vigor are sometimes good 



laj'ers, but good vigor as a rule is essential. 



3. (a) Careful trapnest egg records, 

 (b) 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. 



I The coefficient of variation, if calculated according to the usual formula C. V.= ^ XlOO, is 

 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. 



