Production of hatching eggs in large breeding specific pathogen free chicken flocks.

概要

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Observation of hatching eggs production was conducted with the chickens of 3 successive generations of 2 lines of specific pathogen free chicken flocks, maintained in a largebreeding during 1980 to 1982.The results described below were obtained.1) There were no significant differences in the age laid the first egg and the age at50% egg production among 2 lines and their successive generations. Ages laid the first eggwere from 135 to 144 days, being 140 days in average. The ages at 50% lay were from165 to 177 days, being 172 days in average.2) Egg production rates reached the maximum of 80% at 200 to 230 days of age exceptthe second generation of one of the lines, of which egg production tended to decrease withtheir age, and the rate became 60 to 65% at 420 to 430 days of age.3) Fertilization rates in each generation were over 90%, and the hatching rates were93.0% in average.4) By grouping the eggs by their weight into 4 classes (S: 50g or less, M: 51 to 55g, ML: 56 to 60g, and L: 61g or more) in each line, there was the tendency that the ratesof S and M were increased while those of ML and L were decreased with their generations.
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