TYPES OF INTENSITY IN RHODE ISLAND REDS 



By F. A. Hays, Research Professor of Poultry Husbandry, and 

 Ruby Sanborn, Research Assistant in Poultry Husbandry 



INTRODUCTION 



Intensity or rate of laying is recognized as of vital importance in breeding 

 for high fecundity. Various methods have been used for measuring intensity, 

 and there is an increasing need for more information concerning the relative 

 merits of the different measures as well as for definite data concerning the rela- 

 tion of intensity to other traits affecting fecundity. 



Hurst (1921) measured intensity on a percentage basis during three periods 

 into which he divided the pullet laying year. He called the period from first 

 pullet egg to March first, the winter period; that from March first to July first, 

 the spring period; and that from July first to the end of the laying year, the au- 

 tumn period. By dividing the number of eggs laid in a period by the days mak- 

 ing up the period, he obtained the intensity on a percentage basis. He states 

 that the annual egg record depends upon high intensity during these three 

 periods, and places the dividing line between genetic high and low intensity at 

 30 per cent. This worker does not report upon the relative importance of the 

 three periods or upon their possible relation to each other. 



Di-yden (1921) used the two highest months in the pullet year as a measure 

 of intensity. He found it possible to increase annual production by selection on 

 this basis. 



Goodale and Sanborn (1922) offer as measures of intensity the egg records of 

 individual months, the production in the initial cycle, and the production during 

 the inter-broody periods. No attempt is made, however, to discover their rela- 

 tive importance. Harris and Goodale (1922) studied the correlation between 

 individual monthly production and production for the remainder of the j'ear in 

 Rhode Island Reds. Their data indicate that production during January shows 

 the most intimate correlation. 



Hays and Sanborn (1927) report the correlation between four measures of 

 intensity and annual egg production. These data show the following values for 

 r: first 60 days vs. remainder of the year, +.3082 + .0121; mean winter clutch 

 size vs. annual record, +.3544 + . 0117; net winter rate vs. annual record, +.4769 

 ±.0104; and annual rate vs. annual record, +.7106 + .0066. These wTiters con- 

 clude that mean winter clutch size is the most specific measure of intensity con- 

 sidered. 



This report is concerned with clutch size in periods throughout the year as 

 a measure of intensity. Data are presented to show the correlation between 

 mean winter and mean spring clutch size, between mean winter and mean sum- 

 mer clutch size, and between mean spring and mean summer clutch size. The re- 

 lation of clutch size during these three periods to four heritable characteristics 

 affecting fecundity is shown by means of the coefficient of correlation. The n.ean 

 clutch size during the individual months of March, April and May is also showTi 

 in relation to the four heritable traits. Finally, the correlations between mean 

 clutch size during six intervals of time and annual production are presented. 



