RATE OF GROWTH OF CHICKS 309 



2. Relation of Egg Weight to Weight of Chicks 



Egg size as measured by weight is of considerable economic importance 

 due to the tendency for the market price to depend in no small degree upon 

 the size of the eggs. 



Egg size is often considered as affecting hatchability. Benjamin (1920) 

 was unable, however, to discover a significant correlation between size and 

 hatchability. Dunn (1922) found no relation between egg size and hatchabil- 

 ity. Halbersleben and Mussehl (loc. cit.) also confirmed Dunn's findings, as 

 was later done by Hays and Sumbardo (1927). From these and other studies 

 it appears very unlikely that egg size does affect hatchability. 



Egg size has been shown by a number of workers to be intimately cor- 

 related with the size of chicks hatched. Benjamin (loc. cit.) presents data to 

 show that chick size at hatching depends upon the size of the egg, and that 

 weight differences observed at hatching tend to persist for a considerable pe- 

 riod of time in White Leghorns. Halbersleben and Mussehl (loc. cit.) show 

 that the weight of chicks at hatching averages 64 per cent of the egg weight, 

 but they do not mention the breed studied. Jull and Quinn (loc. cit.) report 

 that Rhode Island Red chicks at hatching average 66.06 per cent of the weight 

 of the eggs hatched. Upp (loc. cit.) reports that Rhode Island Red chicks 

 average 68 per cent of the weight of the eggs hatched. Upp also notes that 

 weight differences in chicks hatched from large and small eggs are observable 

 at two weeks of age, but that such differences have disappeared by the age 

 of four weeks. 



Table 2. — Range in Egg Size of Female Breeders 



In Tables 2 and 3 are given data collected on the Massachusetts Station 

 flock from 1925 to 1928. Both hens and pullets were used for breeding each 

 year reported. The tables show the grouping of the various mothers with 

 respect to egg size during the hatching season, together with the mean weight 

 of their chicks at hatching, at four weeks and at 21 weeks of age. 



Table 2 indicates that the dams of the chicks whose weights are reported 

 ranged in egg size from 48.5 grams (20 oz. eggs) to 60.4 grams (26 oz. eggs). 

 A total of 623 dams was reported on, from which 3645 hatching eggs w'ere 

 weighed. Only about 6 eggs from each hen were weighed at the beginning of 

 the hatching season to obtain an index of her egg weight. Weights at. two 

 weeks of age were recorded on only a small percentage of the chicks each 

 year, while four-week weights were taken on all chicks each year. The num- 

 ber of birds weighed at 21 weeks is smaller than at four weeks because of 

 mortality and because certain undesirable families were discarded previous to 

 the 21-week weighing. 



