RELATION OF INTENSITY TO EGG WEIGHT 

 AND EGG PRODUCTION 



By F. A. Hays, 

 Research Professor of Poultry Husbandry 



Introduction 



Intensity or rate of laying is one of the most important inherited characters 

 affecting egg production. Pearl (1912) developed a theory on the mode of in- 

 heritance of high egg production in which he emphasized the importance of winter 

 production. Goodale (1918) was the first investigator to point out the importance 

 of high intensity in breeding for egg production. Dryden (1921) emphasized the 

 importance of intensity in relation to annual egg production. Hurst (1921) 

 reported that high winter rate depended upon a single dominant gene. Hays 

 (1924) pointed out that high winter rate depended upon two dominant comple- 

 mentary genes. Hays and Sanborn (1927a) stated that mean winter clutch size 

 was a very satisfactory measure of intensity and showed that clutch size was 

 governed in inheritance by two dominant genes. Knox, JuU and Quinn (1935) 

 recommended gross winter rate as one of the most useful measures of intensity. 

 Lerner and Taylor (1936) consider net winter rate obtained after deducting pauses 

 of seven or more days as the best approximation of the winter rate of laying. 



The relation of intensity to egg size has been studied. Atwood (1923) showed 

 that there was a significant correlation ranging from —.13 to —.88 between 

 mean monthly production and mean monthly egg weight. Hays (1930a) re- 

 ported a correlation of —.3157 + .0164 between mean clutch size to January 1 

 and mean egg weight for the same period. Hays (1934) found a correlation of 

 .3001 + .0314 between winter clutch size and time to standard egg weight in 

 Rhode Island Red pullets. 



The importance of high intensity in relation to egg production has been in- 

 vestigated by a number of workers. Hays and Sanborn (1927a, 1932) emphasized 

 the importance of high intensity in breeding for high egg production. Hays and 

 Sanborn (1927b) reported a partial correlation of .4944 ± .0101 between winter 

 clutch size and annual egg production. Knox, JuU and Quinn (1935) found the 

 correlation between rate of laying up to March 1 and annual production to be 

 about .62 in White Leghorns and Rhode Island Reds. Taylor and Lerner (1935) 

 consider the rate of laying to be one of the most important characters in breeding 

 for egg production. Jull (1940) showed the association of high winter rate with 

 annual egg production in a flock of 946 Rhode Island Reds. Tomhave (1941), 

 by selection for high intensity, was able to show significant progress. 



Data Available 



The data included in this report are intended to furnish more complete in- 

 formation concerning the relation of intensity to egg weight and egg production 

 in Rhode Island Reds bred for high fecundity. The birds used in the study in- 

 clude six generations hatched from 1937 to 1942. All records are based on the 

 pullet year, beginning with the first pullet egg and terminating in 365 da)s. 



