MASS. EXPERIMENT STATION BULLETIN 329 3 



The standard deviation in hatching date was high because about the same 

 number of birds was included in each hatch. The mean pause duration in this 

 population, made up entirely of birds with pause, was about 37 days. This 

 is a long period of nonproduction occurring at a time when birds in production 

 are laying at a high rate. Economically, this cessation of production is very 

 important because egg prices are likely to be high in winter. The pause standard 

 deviation is extremely high and the actual range in pause duration was from 4 

 to 123 days. 



The coefficient of correlation measuring the association between hatching 

 date and duration of pause is of some significance. Its squared value, however, 

 indicates that less than 6 percent of the variation in length of pause is due to 

 differences in hatching date. The conclusion must be drawn from these data 

 that the range in hatching dates considered had very little effect on pause 

 duration, and that other factors of greater importance must have been oper- 

 ating. Taken by hatches, there was an average decline in length of pause of 

 about 20 days between the first and the last hatches. 



2. Age at First Egg and Pause Duration 



Hays and Sanborn (1926) reported a correlation of -.2329 + .0138 between 

 age at first egg and pause duration. This constant was obtained on 2134 birds 

 hatched between March 25 and May 15. In the present study the hatching 

 dates were three weeks earlier. It would seem probable from these earlier 

 studies that laying at an early age might increase the length of pause. It 

 should be noted that the mean age at first egg of the birds previously reported 

 was 203 days while the mean age of the birds in this study was 190 days. The 

 693 birds with pause were tabulated and the following constants obtained: 



Number of birds . . . . 

 Mean age at first egg, days . 

 Age standard deviation, days 

 Mean pause duration, days . 

 Pause standard deviation, days 

 Coefficient of correlation 



693 



190.30 



±21.76 



37.11 



±24.31 



.0323 ±0256 



The regression of pause duration on age at first egg was found to be linear by 

 Blakeman's test. The coefficient of correlation was of insignificant magnitude, 

 suggesting no relation between age at first egg and duration of pause. The 

 percentage of birds with pause in the earlier report was lower than in this study, 

 the means in the two groups being 63 percent and 69 percent, respectively. 

 Apparently earlier hatching has overcome the relation between age at first 

 egg and pause duration that was observed in the earlier studies. 



3. Weight at First Egg and Pause Duration 



Poultrymen often express the view that pullets may stop laying during the 

 winter season because they lack sufficient reserve to keep laying throughout 

 the winter. Reserve is difficult to measure, but the assumption might be 

 made that heavy body weight is an indication of reserve. Hays and Sanborn 

 (1926) found no correlation between body weight at first egg and duration of 

 winter pause. Since no other measure of reserve has been suggested, however, 

 the coefficient of correlation between body weight at first egg and pause 



