16 MASS. EXPERIMENT STATION BULLETIN 420 



Necropsy Record for Males and Females from Six Months 

 to Eighteen Months of Age 



This period constitutes the first laying year in the females. The period begins 

 with the onset of sexual maturity in both sexes and is terminated by the annual 

 molt in both males and females. This is a part of the life span of the female 

 that is most important from the standpoint of egg production. The data are 

 summarized in table 3 to bring out possible sex differences and to show any 

 changes through an 8-year period of observation. 



Reference may first be made to the incidence of the avian leukosis complex 

 during the adult period. In the generation hatched in 1935 the incidence was 

 from 10 to 16 percent in the females. Adequate numbers of males were not sub- 

 mitted for necropsy. In 1936 the incidence of the complex changed little. In 

 1937 the complex appeared in the high mortality line for the first time. In 1938, 

 however, there occurred a very high incidence of the conrplex amounting to 

 more than 40 percent in both males and females of the control group. In the 

 next generation the incidence in control females was 8.57 percent and there has 

 been a rather regular increase since then up to 26.92 percent in females in 1942. 

 This disease complex was not discovered in control males during the last four 

 generations. The incidence of the avian leukosis complex has been rather low 

 in both high and low mortality lines, but the numbers of birds concerned have 

 been too small for statistical significance. In the miscellaneous group a general 

 parallelism with the control group may be noted. Males in the miscellaneous 

 experiments showed a higher incidence than the males of the control series. In a 

 general way, these data point to a cyclical behavior in the incidence of the avian 

 leukosis complex through the period of observation and is in agreement with 

 the observation of Bostian and Dearstyne (1944). 



Miscellaneous tumors not considered to be associated with the avian leukosis 

 complex were far more numerous in females than in males. Disorders of the 

 digestive system were a common cause of mortality during the experimental 

 period, and were more frequent in females than in males. Kidney disorders 

 were about as important as digestive disorders and were somewhat more prevalent 

 in females. Reproductive disorders were confined to the females where they 

 represent a major cause of death. Staphylococcic infections have been of rather 

 frequent occurrence in the flock, and more prevalent in males than in females. 

 Such infections probably' gain entrance to the body through wounds. One com- 

 mon type of this disease is bumble foot. Parasites have not been prominent in 

 the flock, probably because of range rotation and because sanitary measures are 

 used to protect the birds. Losses from injury were small and have been largely 

 controlled by careful management. Respiratory diseases have been of little 

 consequence in the flock and are therefore grouped with the miscellaneous dis- 

 orders, which include all not listed in the table. These miscellaneous disorders 

 have affected a significant percentage of birds. Cannibalism is a common vice 

 in flocks bred for high egg production and is greath' modified bj- environment. 

 The actual eating of blood and flesh is much less common in males than in fe- 

 males. Numerous males are lost from fighting and these have been included 

 under cannibalism for lack of a better classification. In the later years of the 

 experiment the apparent increase in cannibalism is probably due to a greater 

 percentage of such birds being sent in for necropsy. 



As already indicated and as pointed out by Bostian and Dearstyne (1944), 

 necropsy records fail to reveal the cause of death in a very significant proportion 

 of dead birds. The birds on which no diagnosis was made on necropsy ranged 



