EFFECT OF HEN PRODUCTION AGE ON EGG COMPOSITION AND EMBRYO DEVELOPMENT IN COMMERCIAL PEKIN DUCKS

At 26, 31, 36, and 42 wk of age, eggs were collected from the same duc k breeder flock to study the effects of hen production age on egg comp osition and embryo development. At each hen age, yolk and albumen meas urements were made on a random subsample of unincubated eggs. Embryo a nd yolk sac measurements were made at 20, 22, 24, 26, 27, and 28 d of incubation. Egg weight was significantly affected by hen production ag e, but most of the observed age effects occurred between 26 and 31 wk with minimal age differences thereafter due to a quantitative feed res triction for egg weight. Yolk weight increased significantly with hen production age, with the largest increase, 6.6 g, also occurring betwe en 26 and 31 wk of age. Yolk-free duckling weight increased with hen p roduction age at 27 d of incubation. The yolk sacs of embryos from the 31-, 36-, and 42-wk-old hens were heavier at 20 and 22 d, before the differentiation in embryo weight. Differences in yolk sac weight were not consistently affected by hen production age between 26 and 28 d of incubation. The eggs from the 42-wk-old hens weighed 3.3 g less than those from the 31-wk-old hens, but yolk-free duckling weight at 27 d w as 2.9 g heavier from the 42-wk-old hens.