Comparison of various characteristics of duration of fertility in hens

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Abstract
1. Maximum duration (Dm, number of days post‐insemination until last fertile egg) and efficient duration (De, number of days post‐insemination until first infertile egg) of fertility, number of fertile eggs (F), dead embryos and hatched chicks (H) during the 21 d following the latter of two intravaginal inseminations (with 125× 106 spermatozoa) on two consecutive days were measured in a total of 2549 layer‐type hens at three ages (starting at 30, 44 and 55 weeks of age). 2. De and Dm were highly correlated (0.46≤r≤0.67). Both De and Dm were also well correlated with F (0.45≤r≤0.80) and H (0.45≤r≤r≤0.29). 3. The highest repeatabilities between hen ages were observed for F (0.34≤r≤0.49) and H (0.36≤r≤0.48) and the lowest for numbers of dead embryos (0.02≤r≤0.28). 4. Because of low fertility 18 d after insemination, the period over which measurements were made could have been reduced by 3 d without significant differences in the ranking of the females. 5. The number of perivitelline spermatozoa found in eggs laid on day 2 is not a good predictor of duration of fertility but could allow the culling of hens associated with lowest De or Dm.
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