CROSSING PRODUCTION AND EXHIBITION BIRDS 5 



Class 2 hybrids, representing the Fi generation from mating production males 

 to exhibition females, are comparable with class 1 hybrids produced by the 

 reciprocal cross. The group of class 2 hybrids showed heavier weight at first 

 egg along with a greater percentage of early maturing birds than appeared in 

 class 1 hybrids. Class 2 hybrids showed lower intensity, somewhat lower hatcha- 

 bility, and a mortality rate about half that of class 1. Class 2 hybrids were equal 

 to class 1 in freedom from winter pause and in winter egg weight, and were 

 decidedly superior in freedom from broodmess, persistency, and to some extent 

 in annual egg production. Class 2 hybrids compared with their checks showed 

 almost the same differences that were observed between class 1 hybrids and 

 checks, except that laying-house mortality was much lower in class 2 hybrids 

 than in their checks. 



Class 3 hybrids are the F2 generation produced by mating of Fi birds. In 

 hybrid matings the F2 generation shows the maximum variability because of 

 segregation of characters. In such crosses as are considered in this report, the F2 

 generation may be inferior to the Fi generation because of segregation of unde- 

 sirable genes and because of high variability in characteristics affecting fecundity. 



Table 2 shows that the F2 pullets were heavier than the checks at first egg 

 but less than half of the birds were early maturing compared with 84.48 per cent 

 early maturing in the checks. In comparison with the checks, F2 birds were also 

 decidedly low in intensity, showed more winter pause, larger winter egg size, 

 lower hatchability, a decreased percentage of non-broody birds, lower persistency, 

 increased mortality, and greatly decreased egg production. 



Class 4 hybrids, produced by mating Fi males to production females, were 

 superior to the checks in body weight at sexual maturity, but their age at sexual 

 maturity was greater and the percentage of genetically early-maturing birds 

 lower. These hybrids were decidedly inferior to the checks in intensity, winter 

 pause, persistency, and egg production; they were superior in egg weight, and 

 about equal to the checks in hatchability, non-broodiness, and mortality rate. 

 Compared with the first hybrid generation, they were superior only in freedom 

 from broodiness and in persistency. 



Class 5 hybrids represent the reciprocal type of mating to class 4; namely, 

 mating production males on Fi females. Daughters produced were somewhat 

 heavier at first egg than check daughters and showed a significantly lower per- 

 centage of early-maturing individuals. They were superior to the checks in in- 

 tensity, non-pause, winter egg weight, and annual egg production. The hatcha- 

 bility of hybrids and checks differed significantly and the percentage of non-broody 

 birds was lower in the hybrids, but the laying-house mortality was very high. 

 Compared with the hybrids of class 4, the class 5 hybrids were greatly superior 

 in intensity and in the absence of winter pause, enabling them to average 229 

 eggs compared with 184 eggs for class 4 hybrids. Class 5 hybrids were decidedly 

 low in vigor as judged by the high mortality rate in the laying houses. 



Class 6 daughters came from crossing exhibition males on Fj females. This 

 generation of hybrids was inferior to their checks in all respects except winter 

 egg size and body weight. They averaged to lay 176 eggs compared with 245 

 eggs for the checks. Compared with the daughters in class 5 where production 

 males were mated to Fi females, they were decidedly inferior except in vigor. 



In class 7 the daughters of production males mated to F2 females are con- 

 sidered. Compared with the checks, these females were smaller at first egg but 



