FERTILITY IN RHODE ISLAND REDS 11 



A study of the 702 pullets in the late-hatched group indicates no relation 

 between winter egg production and fertility. In the early-hatched group there 

 was a slight tendency for the very heavy winter layers to exhibit lower fertility 

 than the average or below-average producers. The data are inconclusive on this 

 point, and further information is desirable. 



5. Relation Between Number of Mates to the Male and Fertility 



The range in number of mates to each male was rather limited in these data. 

 The number of females in each mating pen varied from 1 to 14, with 8 to 10 

 being the most common number. It is desirable to see whether, within these 

 limits, there was any significant relation between the number of females mated to 

 a male and fertility. The percentage of unsuccessful matings was considered 

 to be the best measure of relationship. 



Table 7. — Percentage of Unsuccessful Matings from Males Mated to 

 Different Numbers of Females 



The data in Table 7 show that a variation from 1 to 14 in the number of females 

 mated to a male had no effect upon fertility in either the late- or the early-hatched 

 groups. In other words, the range in number of females used was inadequate to 

 test the fertilizing power of the males. The wide fluctuations in percentage of 

 unsuccessful matings are apparently due both to selective matings and to germ 

 cell incompatibility. No data are available on the relative importance of these 

 two factors. 



6. Progress in Improving Fertility 



Throughout the period covered by these .studies, selective breeding for high 

 hatchability and for large families was constantly practiced. If fertility were an 

 inherited trait it is conceivable that fertility would have shown an increase as 



