8 MASS. EXPERIMENT STATION BULLETIN 307 



last eight years, in the absence of specific disease outbreaks, have fallen as low 

 as 15 per cent in only one year. Experience and observation indicate that a 

 laying-house mortality above 15 per cent is excessive. It is probable that selec- 

 tion of breeders for low family mortality has not been rigid enough because of 

 efforts to establish other desirable characters. Another possibility is that, since 

 no outside stock has been introduced since 1915, the flock may be restricted to 

 too close relationships even though inbreeding has been avoided. There is no 

 experimental proof to support this possibility, however. 



The last double column gives the mean percentage of fertile eggs hatched, 

 together with the number of females used (in parentheses). Hatchability has 

 improved very slightly during the whole period. It seems probable that more 

 attention should be given to this character in the selection of breeders. 



The Relation Between Fecundity Characters and Egg Production 



Goodale and Sanborn (1922) pointed out that there are five prominent character- 

 istics that tend to increase the annual egg production of Rhode Island Reds. 

 These characters are early sexual maturity, high intensity, no winter pause, non- 

 broodiness, and high persistency. Hays (1924 and 1927) showed that these 

 characters are inherited and that a total of eight genes is concerned. If the 

 five characters are considered as units, there are thirty-one types of birds each 

 representing a different combination of the five. There are five types of individ- 

 uals each carrying one of the five desirable characters; ten t}pes, each carrying 

 two desirable characters; also ten types, each carrying three desirable characters; 

 five types, each carrying four desirable characters; and one type having all five 

 desirable characters combined. A rough measure of the degree of improvement 

 in the flock for egg production would be the percentage of birds combining either 

 four or five of these desirable characters. Table 2 shows that the average egg 

 record of birds increases as the number of desirable characters increases. The 

 table includes 2300 birds hatched from 1928 to 1932. 



» 

 T.\BLE 2— Rel.\tion of Number of Desirable Characters to 

 Annu.al Production. 



Table 2 shows that the 31 birds classed as having neither early maturity, high 

 intensity, no winter pause, non-broodiness, nor high persistency averaged 149 

 eggs, showing that they must have been maintained under good laying conditions. 

 No doubt a number of these individuals are improperly classified because of the 

 variability in each character that always occurs. The table shows further that 

 the group of 158 birds carrying only one of the five characters averaged to lay 

 about 157 eggs. From this class on, the addition of any one character increased 



