320 MASS. EXPERIMENT STATION BULLETIN 269 



Further reference to Table 7 brings to light the fact that body weight of 

 pullets at 21 weeks of age is not an index of vigor. The table clearly shows 

 that the mortality rate for pullets weighing 4.5 pounds or over at 21 weeks 

 was substantially the same as for pullets weighing under 4.5 pounds at the 

 same age. The table also indicates that 4.5 pounds is a rather high standard 

 of weight for pullets of the flock studied, because less than one-third (31 

 per cent) of the birds actually fell into the large class. These data are in 

 agreement with previous data reported by Hays and Sanborn (1928 loc. cit.) 

 to the effect that weight at first egg (about 180 days) is independent of 

 mortality rate in the laying houses. 



From the standpoint of vigor, the data in Table 7 indicate: First, that 

 heavy weight at 4 weeks of age does indicate superior vigor in pullets; and 

 second, that heavy weight at 21 weeks of age is not a criterion of vigor. 



E(/g Production 



A study of the mean annual egg records of pullets in the large and small 

 weight classes at 4 weeks of age suggests a slight superiority in the large class 

 in the first four years reported. However, when the mean annual production 

 of the 1605 birds clastsed as small is compared with the same figure for the 

 1370 birds classed as large at the end of the table, all differences disappear. 

 The actual average annual egg records are 195.3 and 195.6 respectively. 



Pullets weighing less than 4.5 pounds at 21 weeks of age exhibit no 

 significant difference in their first-year egg records from pullets weighing 4.5 

 pounds or more at 21 weeks. The mean egg record of 1973 birds in the first 

 class is 195.5 eggs: and for the 955 birds in the second class, 194.9 eggs. On 

 the basis of these data, neither four-week weights nor 21-week weights furnish 

 any criterion of future egg yield. 



Summary 



1. The normal weights of Rhode Island Red chicks in the Massachusetts 

 Agricultural Experiment Station flock are 36.7 grams (.08 lb.) at hatching; 

 87.9 grams (.19 lb.) at 2 weeks; 214.1 grams (.47 lb) at 4 weeks; 1390.0 grams 

 (3.06 lbs.) at 16 weeks; and 2126.9 grams (4.69 lbs.) at 21 weeks. 



2. The dams of a part of the chicks used in these studies are grouped 

 in classes with respect to their egg weight during the hatching season. Chick 

 weight at hatching varied from 33 grams for the small egg dams, up to 38.7 

 grams for the large egg dams. The weight differences in these chicks persisted 

 at 4 weeks of age, when the chicks from the large eggs were 26.9 per cent 

 heavier than the chicks from the small eggs in the extreme classes. At the 

 age of 21 weeks, weight differences in chicks hatched from large and small 

 eggs had disappeared. 



3. Hatching date ranging over a 49-day jaeriod affected the weight of 

 chicks throughout most of the growing season. The difference in mean hatch- 

 ing weight of the chicks in the first and last hatches was not striking, but 

 the early hatched chicks were 12.98 per cent heavier than the late hatched 

 chicks at 2 weeks of age, 28.79 per cent heavier at 4 weeks of age, 21.70 per 

 cent heavier at 16 weeks of age, and 17.12 per cent heavier at 21 weeks of 

 age. 



