Two flocks of broiler breeder hens, differing in uniformity of body weight, were evaluated under cage and floor management systems over a 28-week period. Hens were housed singly in cages (N = 280) or in litter floor pens (N = 304). Caged hens were artificially inseminated with .05 ml of pooled semen once weekly. Floor birds were mated naturally. During the first 10 weeks of production, the more uniform flock exhibited significantly higher egg production than the less uniform flock. Uniformity did not influence cumulative egg production, egg weight, fertility, or mortality. Initial egg production was similar for caged and floor housed hens, but the caged birds attained significantly higher egg production during peak production. Caged females showed higher egg weights and body weights than did the floor females throughout the study. Naturally mated birds attained significantly higher fertility than artificially inseminated birds (94.9 vs. 90.6). Correlation coefficients for the weights of caged hens at 20 and 24 weeks with 24, 32, 40, and 50 week weights, total eggs per bird, and age at first egg indicated that body weight at 24 weeks was a better indicator of subsequent flock performance than was body weight at 20 weeks.
The literature pertaining to linkage relationships in the chicken has been reviewed. A new linkage map is proposed consisting of 13 linkage groups. In cases where nomenclature has been duplicated, new symbols are proposed. A tabular summary of linkage tests which have shown independent segregation is included.
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