Three experiments were performed, involving 18, 16 and 48 flocks with 9-16 females and 0-4 males per flock. The White Leghorn strains used had been selected either for egg mass or age at sexual maturity, or were unselected. Age at 50% egg production, rate of lay, survival rate, egg weight, egg mass and body-weight gain from 20 to 50 wk of age were the traits studied. Effects of genetic stocks, time elapsed after flock assembly, developmental age and laying-house environment (cage v floor pens) were also examined using a factorial experimental design. Strains within systems of selection differed significantly for body-weight gain only. Mean body-weight gains from 20 to 50 wk of age were 317.0 and 379.6 g (P <0.005) and females kept in the presence and absence of males resp. The corresponding mean egg weights were 56.4 and 57.0 g (P <0.10). Pullets kept in colony cages were older (P <0.005) when 50% egg production was attained than pullets kept in floor pens, and had a lower (P <0.1) survival rate; rate of lay and egg mass were lower (P <0.1) and egg weight was greater (P <0.1) in colony cages than in floor pens.
|Publication Title||Applied Animal Ethology|
|Author Address||Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas 66506, USA.|
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