Breeding

Extract

1. 1. The connection between the rate of maturity (number of days between birth and production of the first egg) and egg production of 938 White Leghorn pullets, hatched and reared on the Experimental farm of the Oliefabrieken Calvé-Delft was investigated. The pullets were of various strains and received widely differing treatment as regards feeding.

2. 2. There is a curvilinear correlation between rate of maturity and to talproduction and also between rate of maturity and winter production. It is, therefore, not correct to calculate with rectilinear correlations or regressions.

3. 3. The conditions, obtaining during the rearing, influence not only the rate of maturity, but also the connection between the rate of maturity and egg production.

4. 4. It is, therefore, impossible to state any generally acceptable rules concerning the way in which the existing connection can be used to raise the average production by the elimination of certain birds.

5. 5. Even when the pullets have been carefully culled either before or at the commencement of production, it is possible to raise the average production still further by eliminating those birds, which come into production last. A considerable number of bad producers are found among the birds with the slowest rate of maturity.

6. 6. No connection was found between rate of maturity and mortality.

7. 7. Neither was there any connection between rate of nlaturity and the average weight of the eggs produced after December.

8. 8. For the 514 birds which began production after 30th September, 1935, a rectilinear correlation of +0.66±0.02 was found between rate of maturity and the average weight of the first ten eggs produced. The regression-eo-efficient of this “inception egg-weight” to rate of maturity in +0.16±0.02.