168 



MASS. EXPERIMENT STATION BULLETIN 242 



These studies were undertaken to discover if the elimination of the broody 

 trait has been inimical to vigor. A total of 2163 birds liatclied in the five 

 years from 1922 to 1926 have been c'Jassified as broody or non-broody. Since 

 the greatest percentage of pullets tend to become broody before July 1, it has 

 been decided to use puMet records up to July 1 for the classification. Those 

 puJlets that actually went broody before JuJy 1 each yeiar are placed in the 

 broody class and all others in the non-broody class. Such classification is 

 faulty in that many birds actually do not show broody behavior by July 1 and 

 a smaller projiortion not until later laying yeairs. For this study siuch crude 

 classification should be of some value. 



Table 9 — Relation of Broodiness to Vigor 



Tabile 9 shows the percentage of birds not going broody before July 1 to 

 be as follows: 1922, 70 per cent; 1923, 75 per cent; 1924, 58 per cent; 192-5, 

 58 per cent; and 1926, 77 per cent. The records for 1924 are valueless be- 

 cause of a severe roup epidemic, but the records for 1925 sihow that the in- 

 crease in broodiness up to July 1 was associated with the lowest mortality rate 

 in the laying houses for a five-year period. 



Table 9 also indicates a consistent and almost parallel decline in mortality 

 rate for both brooi^ies and non-ibroodies up to 1925. The records for 1926 

 assign a mortality i^ate after July 1 of 1.92 per cent for broody birds and 

 15.10 per cent for non-broody birds. This very abrupt increase in mortality 

 in the non-broody group cannot be considered normal and cannot be ex- 

 plained. The mortality rate in the non-broody group is greater than for the 

 broody group in the four normal years reported. 



The total mortality rate for five years is 5.19 per cent in the broody group 

 and 10.89 per cent in the non-broody group. If records for the epidemic year 

 1924 are omitted, the mortality' rate for broody birds is 4.42 per cent, and 

 for non-broody birds 11.33 per cent. Omitting 1926, the broody group show 

 a mortality of 5.76 per cent and the non-broody group 9.57 per cent. These 

 data indicate that the manifestation of broody behavior before July 1 of the 

 pullet laying year is an indication of superior vigor and that the elimination 

 of the broody trait in this flock has been accompanied by greater mortality 

 rate in the laying houses. 



