CHANGES IN EGG PRODUCTION. 



Ill 



Data on the initial cj^cle, winter pause, spring production, summer pro- 

 duction, date of last egg and rate of production are restricted to certain 

 years, because breeding for changes in these characteristics has neces- 

 sarily been secondarj'. They indicate clearly such changes as have oc- 

 curred. For purposes of claritj^, intermediate years are omitted in cer- 

 tain graphs. 



Changes in Mean Winter Egg Production. 



Winter egg production is defined as the number of eggs laid prior to 

 March 1 in the first lajing (pullet) year. In Table II, represented graphi- 

 cally in Fig. 5, is given the mean winter production of the flocks from 

 1912 to 1920, inclusive. A high-line strain, as a definite entity, was not 

 propagated until 1917. From 1917 on, the winter production given in 

 the table and graph is that of the high line. A low line, L-L ^, Fig. 5, was 

 propagated in a small way for a time, but finally lost. In 1917 a point 

 is indicated for comparison with the high line which is the weighted pro- 

 duction of a flock bred primarily for absence of broodiness, and in whose 

 establishment all non-broodies available, high producers or low, were 

 mated with three males : No. 300.3; his son. No. 5470, by his sister; and 

 his grandson, sired by No. 5470 out of an unrelated bird with a good 

 record. The sisters of No. 3003 were noted for very low production in 

 addition to non-broodiness. The average winter egg production of the 

 daughters of No. 3003, as well as of the daughters of No. 4128, another 

 low male of separate origin, is indicated for further comparison. 



Graphic representation of the improvement made is shown by integral 

 curves for each j-ear as given in Fig. 6, while frequency polygons for winter 

 egg production for certain j^ears are given in Fig. 7, the statistical con- 

 stants being given in Table III. 



Table III. — Statistical Constants for Certain of the Flocks. 

 Winter Egg Production. 



Yeab. 



Num ber 



of 



Birds. 



Mean.i 



Standard 

 Deviation. 



Coefficient 

 of Variation. 



1913-14 

 1915-16 

 1918-19 

 1919-20 

 1920-21 



171 



237 

 109 

 124 

 160 



36.70± .88 

 29.86± .76 

 63.61±1.27 

 58.56±1.45 

 67.34*1.33 



17.05* .62 

 17.40± .54 

 19.62± .90 

 23.93±1.02 

 24.88* .94 



46.45*2.03 

 58.27*2.34 

 30.85*1.54 

 40.87*2.02 

 36.94*1.57 



Ajtnual Egg Production. 



1913-14 

 1915-16 

 1918-19 

 1920-21 



34.66*2.15 

 40.20*1.32 

 29.89*1.78 

 39.78*1.82 



41.06*2.95 

 33.17*1.20 

 43.31*3.03 

 33.15*1.67 



> Means calculated from grouped data instead of ungrouped as in Table II. 



