CROSSING PRODUCTION AND EXHIBITION BIRDS 3 



greater in the exhibition line. In the birds tested, hatchability was very much 

 higher in the production line. The proportion of non-broody birds, measured 

 by first-year records, was essentially the same in the two lines. The percentage 

 of highly persistent birds was nearly three times as great in the production line 

 as in the exhibition line. The mortality rate for 365 days in the laying houses 

 was significantly higher in the production line. Mean annual egg production was 

 about 207 eggs for production birds compared with 130 eggs for exhibition birds. 

 Table 1 shows in general that the production line was superior for early sexual 

 maturity, intensity, hatchability, persistency, and annual egg production. The 

 exhibition line excelled in egg size and for low laying-house mortality only. 

 Differences in body weight at first egg are of questionable significance because of 

 great differences in age at first egg. 



CHARACTER OF HYBRIDS 



Hybrids produced were derived from the following classes of matings: 



1. Exhibition males X production females [ Fi 



2. Production males X exhibition females j 



3. F2 generation. 



4. Fi males X production females. 



5. Production males X Fi females. 



6. Exhibition males X Fi females. 



7. Production males X F2 females. 



8. Exhibition males X F2 females. 



9. Miscellaneous hybrid matings. 



Check birds include the general flock bred for high fecundity in the same year 

 or years in which the different hybrid matings were made. All birds were hatched, 

 reared, and housed together in order to reduce the effects of environmental 

 influences. In Table 2 the data are summarized for comparative study. Some 

 interesting differences are shown between the various classes of hybrids and the 

 checks, which represent production-bred lines. 



Class 1 hybrids, representing the Fi generation from mating exhibition males 

 to production females, were decidedly superior to the checks in body weight at 

 first egg, showing the effects of heterosis. Early sexual maturity was observed 

 in a greater percentage of the check birds than of the Fi daughters, which ac- 

 counts in part for the greater weight of the hybrids at sexual maturity. The 

 hybrids were not quite equal to the checks in intensity, but there was very little 

 difference between the two groups with respect to pause. Winter egg weight was 

 decidedly greater in the hybrids, and their eggs averaged slightly over 24 ounces 

 per dozen up to January 1. Of the birds tested, the hybrids were slightly superior 

 to the checks in hatchability. The percentage of non-broody birds was somewhat 

 less in the hybrids than in the checks. Persistency was decidedly lower in the 

 hybrids, suggesting either that persistency was not well established in the pro- 

 duction birds or else that dominant genes for low persistency were transmitted 

 by the exhibition parents. Mortality rates in the laying houses were very similar 

 in hybrids and checks, certainly not showing a difference great enough to be 

 significant. In annual egg production the hybrids fell below the checks, due in 

 large measure to greater age at sexual maturity, lower intensity, more broodiness, 

 and greatly reduced persistency. 



