WINTER PAUSE IN RHODE ISLAND REDS 



By F. A. Hays, Research Professor of Poultry Husbandry 



A cessation of laying for four or more successive days during the winter 

 months of the pullet year is called a winter pause in this report. The time 

 limits considered lie between November 1 and March 1. These periods of 

 nonproduction are of great economic importance. Some years ago Hays and 

 Sanborn (1926) showed that nonpause birds averaged to lay 16 more eggs in 

 the pullet year than pause birds. As new high levels of egg production are 

 being attained by selective breeding, the control of the winter pause becomes 

 even more important. Difficulties in separating the effects of inheritance from 

 the effects of environment upon winter pause have been pointed out many times 

 by this laboratory. This is a report of a further attempt to discover factors 

 that may affect winter pause so that methods may be worked out for its control 

 or elimination. 



The birds used in these studies include production-bred Rhode Island Reds 

 used in different experiments. The birds used in section 4 were hatched in 

 1926 and represent the last flock on which hourly trapnest records are available. 

 The birds used for study in all of the other sections were hatched in 1933 and 1934. 



1. Hatching Date and Winter Pause 



Date of hatching is known to have a definite effect on pause duration. Within 

 recent years there has been an ever-increasing amount of early hatching, so 

 that many pullets are hatched in February or March. With this early hatching, 

 production-bred pullets that normally begin laying at about six months of age 

 will begin their laying year in August. Observations indicate that the great 

 majority of these birds will stop laying before March 1 and many will undergo 

 a partial molt. 



The relation between hatching date and presence or absence of pause and the 

 effect of hatching date on pause duration were studied in a total of 1,006 

 pullets hatched in eight weekly hatches between March 4 and April 23 in 1933 

 and 1934. Winter pause appeared in the following percentages of birds in the 

 eight hatches: Hatch 1, 76.9; hatch 2, 77.0; hatch 3, 75.3; hatch 4, 81.5; 

 hatch 5, 68.2; hatch 6, 64.4; hatch 7, 59.4; and hatch 8, 55.9. Apparently 

 the proportion of birds that exhibit pauses of four or more days was less in the 

 April hatched pullets than in those hatched in March. 



In order to determine the relation between hatching date and pause duration, 

 the coefficient of correlation was calculated on the 693 individuals with winter 

 pause. The regression of pause duration on hatching date was found to be 

 strictly linear by Blakeman's test. The constants obtained are as follows: 



Number of birds 



Mean hatching date .... 

 Hatching date standard deviation, days 

 Mean pause duration, days . 

 Pause standard deviation, days . 

 Coefficient of correlation 



693 



March 29 



±15.19 



37.11 



+ 24.31 



.2366 +.0242 



