186 



TECHNICAL BULLETIN 8 



Number of birds 



Mean length of winter pause 



Winter pause standard deviation 



Mean annual production . . . . 



Annual production standard deviation 



Coefficient of correlation . . . . 



Regression of winter pause on production . 



Regression of production on winter pause 



134.8 

 32.39 



±21.77 

 172.51 



±41.07 

 —.2107 

 —.112 

 — .3f)8 



.0176 



Tiie mean annual record of the pause birds throughout the period is about 

 17o eggs. The range of variation in annual egg yield is wide, as is shown by 

 its standard deviation. Greater homogeneity in heritable factors conceraed 

 in fecundity should reduce such variability. 



The magnitude of the coefficient of correlation is sufficient to indicate that, 

 in general, an mcrease in length of winter pause is accompanied by a de- 

 crease in annual egg production. The time lost in winter pause is not com- 

 pensated for by heavier production either before or after the pause in any 

 class of pause birds. 



27. Correlation Betiveen Jnnval Production BeloK' the Mean and the Pres- 

 ence of Winter Pause for the Total Poijulation. 



Coefficient of correlation 



-f.3056 ± .0132 



Low annual production is signilicantly correlated witli the presence of 

 winter pause as shown in the above table. Even though such a short period 

 as a four-day pause is considered, this correlation coefficient is of appreci- 

 able magnitude. Winter pau.se must, tiierefore, be classed as inimical to 

 highest annual egg yield, for the pause birds averaged but 173 eggs while 

 the non-pause group averaged 189 eggs. 



Gkneral Discission axu Su.mmary. 



The length of the winter laying cycle is unquestionably modified by a 

 series of environmental influences. Some of these influences are within 

 while others are beyond control of the poultry breeder. Winter pause is the 

 complement of the winter laying cycle and is important in that it vitally 

 aifects total fecundity. 



Two distinct classes of pullets appear in the flock studied, namely, pause 

 and non-pause. A group of pause birds studied beside a group of non- 

 pause birds, both groups hatched on the same date and lioth groups starting 



