FACTORS AFFECTING FERTILITY IN RHODE ISLAND REDS 



By F. A. Hays, Research Professor, and Ruby Sanborn, Research Assistant, 

 in Poultry Husbandry 



Introduction 



Fertile matings in domestic fowl may be defined as the bringing together by 

 natural means of compatible sperm and compatible ova so that union of sperm 

 and ovum takes place. Studies on fertility have shown that the process of fertili- 

 zation is physiologically complex and that the fusion of a single sperm with a 

 single ovum depends upon many coordinated functions. 



Data at the Massachusetts Station indicate that a significant number of 

 embryos die, probably during the first day of incubation, very likely due to 

 zygotic lethals. Such embryos are too little developed to be recognized by 

 ordinary candling methods so that the eggs are considered infertile. A cytological 

 examination of the embryos in serial sections, however, shows definite embryonic 

 development. It is therefore probable that the technique for classifying eggs as 

 fertile or infertile needs to be modified. 



Satisfactory fertility is a basic necessity in all poultry breeding operations. 

 Progress in pedigree breeding depends largely upon high fertility to produce 

 large families of birds for trapnest records and for the breeding test. Although 

 experimental evidence indicates little or no association between high fertility 

 and high hatchability, adequate reproduction very definitely depends on high 

 fertility. 



This report includes a study of the behavior of fertility in a breeding program 

 extending over a fifteen-year period. Consideration is given to a number of 

 controllable breeding practices as well as to evidence regarding the inheritance 

 of fertility. 



Data Available 



Data used in these studies include 2,201 Rhode Island Red females ranging 

 in age from one to five years and 305 males ranging in age from one to four years. 

 The data are divided into two groups. In the late-hatched group the chicks were 

 hatched at weekly intervals between March 25 and May 15 during the years 

 1922 to 1932. The records for 1926 were omitted because in that year the eggs 

 were dipped into a creosote disinfectant before incubation, and this caused the 

 death of many embryos. The early-hatched group was hatched in eight weekly 

 hatches between March 4 and April 27 from 1933 to 1936. Fertility records 

 of individual females are included only if they laid eight or more eggs during the 

 breeding season. 



1. Relation Between Temperature and Fertility 



The mean of outside daily temperatures reported at the College during the days 

 that the hatching eggs were laid for each hatch were calculated. In the late- 

 hatched group these records began February 22 and in the early-hatched group, 

 February 1. In both cases the first collection period and temperature record 

 covered about ten days and all later collection periods and temperature records 

 covered seven days. 



