14 MASS. EXPERIMENT STATION BULLETIN 344 



For purposes of comparison all the daughters in the three lines have been 

 divided into three groups with respect to time to standard egg weight. Those 

 attaining standard egg weight in from to 30 days are fast; those requiring 

 31 to 60 days, medium; and those requiring 61 days or longer, slow. Table 

 3 shows the summarized results of this classification. 



Table 3. — All Daughters Classified According To time 

 Required to Attain Standard Egg Weight 



Fast 



Medium .... 

 Slow 



The data indicate that line A daughters fell predominantly in the slow class. 

 Line B showed about half the daughters to be fast, with one fourth medium 

 and one fourth slow. Line C had equal numbers of fast and slow, and about 

 half as many in the medium class. The fact that line C carried so many birds 

 in the slow class is a further indication of the occurrence of small-egg genes in 

 this group. The fact should be kept in mind, however, that this classification 

 includes only daughters that did attain standard egg weight. The following 

 study on the character of daughters produced by fast, medium, and slow dams 

 will throw some light on their relative value for breeding. 



Breeding Value of Fast, Medium, and Slow Dams 



Records on time required to standard egg weight are available on only part 

 of the dams and daughters. Available data are summarized in Table 4, and 

 may be assumed to approximate the true situation. 



Fast dams were used for breeding in lines B and C. In Line B these dams 

 produced fast, medium, and slow daughters in the proportions of about 2-1-1. 

 In line C fast dams gave the three classes of daughters in the proportions of 

 about 2-1-2. Medium dams were used in all three lines. In line A, the three 

 types of daughters occurred in proportions of about 1-1-1.5. 



Line B daughters from medium dams occurred in approximately 2.5-1-1 pro- 

 portions. In line C the medium dams gave daughters in about 2-1-1.5 propor- 

 tions. Slow dams in line A gave, daughters in about the ratio of 1.5-1-3. In 

 line B the ratio of the different kinds of daughters was about 1-1-1. Only one 

 dam of the slow class occurred in line C. This dam gave only slow daughters. 

 There were three dams that did not attain standard egg weight during the first 

 year. These were all in line A and gave the three kinds of daughters in propor- 

 tions of about 1-2-5. 



A general survey of the breeding results from the three classes of dams with 

 respect to time to standard egg weight shows that the time required depends 

 on inheritance. There is a general parallelism between time required to attain 

 standard egg weight and egg size. The data are suggestive of more than one 

 dominant gene operating to reduce the time interval and possibly of an epistatic 

 gene lengthening the time to standard egg weight. The selection of females 

 for breeding purposes should be made on the basis of ability to lay standard- 

 weight eggs within sixty days from the first pullet egg. 



