RATE OF GROWTH OF CHICKS 311 



which they were hatched than was observed at four weeks of age. In fact, 

 the differences in weights of both males and females in the different egg 

 weight cJaisses are so slight as to be statistically insignificant. When both 

 sexes are considered together, the birds from the 22-ouince eggs show the 

 same mean weight as those from the 26-oimce eggs. Birds from 22 to 26 

 ounce eggs are about 9.1 per cent lieavier than birds from 20 and 21 ounce 

 eggs. 



In general, these data indicate that weight differences in chicks at hatch- 

 ing are not persistent, and that such differences in Rhode Island Reds will 

 disappear by the time the birds are about 21 weeks of age. 



3. Relation of Hatching Date to Weight of Chicks 



Date of hatching has a significant effect upon the weight of growing 

 chicks as has been pointed out by Hays and Sanborn (1924) and others. The 

 data reported in Table 4 cover available records on Rhode Island Reds from 

 1918 to 1928 and are the same records reported in Table 1 but regrouped ac- 

 cording to hatching date. It will be noted that the range in hatching dates is 

 but 49 days, since there were eight weekly hatches on corresponding dates 

 each year. Effects of hatching date upon weight would probably be more 

 pronounced if longer hatching seasons had been employed. 



Weight at Hatching 



The summary for the six-year period at the end of Table 4 does not in- 

 dicate a very important relation between date of hatching and weight of chicks 

 when hatched. There does appear to be a slight decline in the weight of the 

 later-hatched chicks in comparison with those hatched earlier, but it is very 

 unlikely that this small difference of slightly more than one gram is significant. 

 The data in hand would seem to indicate, therefore, that within the limits of 

 the 49-day range in hatching dates considered no effect on hatching weight 

 might be expected. 



Weight at Two Weeks of Age 



The effects of hatching date upon chick weight begin to be noticeable at 

 two weeks of age. The summary in Table 4 shows that the first two hatches 

 averaged 94.85 grams, while the last two hatches averaged 83.95 grams. The 

 chicks in the first two hatches were 12.98 per cent heavier than those in the 

 last two hatches. There is observable a rather consistent decline in weight as 

 the hatching date becomes later, especially after April 15. Just why the 

 earlier chicks should attain more weight at the age of two weeks than do the 

 later chicks is not clear. 



Weight at Four Weeks of Age 



The summary for Table 4 illustrates the perfect consistency of the rela- 

 tion between hatching date and chick weight at four weeks. The weight re- 

 cords include 17868 chicks so that the data are adequate for the purpose. A 

 seven-day increase in hatching date is accompanied by a decrease in chick 

 weight, ranging from 8.4 to 17.9 grams. For the 11-year period reported, the 

 first hatch chicks averaged 28.79 per cent heavier than the last hatch chicks. 

 There can be no question, therefore, that under Massachusetts conditions. 



