MORTALITY STUDIES IN R. I. REDS 5 



The method of management was essentially as follows: All chicks were taken 

 from the incubator to 10 x 12 coal-heated brooder houses on the range. A four- 

 year range rotation was regularly used. Chicks from all experiments were hatched 

 and housed together, usually about 225 in each house. The sexes were separated 

 at eight weeks of age and the males removed to summer shelters while the pullets 

 remained in the original houses. As pullets approached sexual maturity in 

 September they were taken to the laying houses. The average age at housing 

 was about six months. Cockerels were taken to winter quarters about the end 

 of September and housed in large units. All chicks received pox vaccine when 

 10 to 12 weeks of age, and all stock was free from pullorum disease throughout 

 the period. No outside birds were ever brought on the premises and visitors were 

 excluded. Some hatching eggs from outside sources have been brought in. In 

 January some breeding pullets were removed to breeding pens, some of them 

 being placed in pens with old hens. Near the end of April these breeding pullets 

 were returned to the laying houses. In June all females were removed to summer 

 lading shelters to complete their first laying year. Cockerels remained in the 

 same quarters up to January and then were shifted about for breeding purposes 

 through the month of April. They were then assembled in larger units until 

 the following fall when the period of observation ended. In the control and 

 miscellaneous groups two or three cockerels from each selected family were 

 retained after 6 months of age. In the high and low mortality lines, however, 

 all cockerels hatched were retained for observation between the ages of 6 and 

 18 months in the last six generations and were housed as one large unit in a 

 separate house from other cockerels. 



EXPERIMENTAL RESULTS 



Consideration will be given first to the mortality phase of this experiment. 

 Mortality rates are considered for three periods: namely, the first 8 weeks, from 

 8 weeks to 6 months of age, and from 6 to 18 months of age. 



Mortality Rates from Hatching to Eiglit Weeks of Age 



In the controls the mortality of all chicks ranged from 2.03 to 7.66 percent, 

 with a mean mortality of 5.21 percent for the seven generations reported. The 

 generation hatched in 1936 was not included because of abnormal losses caused 

 by fire and accident. No consistent change in the mortality rate was observed 

 through an eight-year period. The high mortality line showed a consistently 

 higher mortality rate than the control line and much higher than the low line, 

 except for the generation hatched in 1938. There is no evidence to account for 

 the excessive losses in the low line in 1938. Mortality rate in chicks in the 

 miscellaneous experiments was intermediate between that of the controls and 

 that of the high mortality line. (Table lA and Chart 1.) 



There is no evidence from these data that selective breeding will reduce young 

 chick mortality. 



Mortality Rates from Eight Weeks to Six Months of Age 



The sexes were separated at 8 weeks of age and the number of males was greatly 

 reduced at that time. The general policy was to retain almost all of the females 

 to the age of 6 months. All mortality rates were based on the number of chicks 

 at the beginning of a period and the number that died during that period. The 

 mortality rates are reported separately for the sexes and for the sexes combined. 



