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Age of Dam: Difference between revisions
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It has been observed that some breeders preferentially treat different age of dams differently resulting in a contemporary group by age of dam interaction on some traits where there is a main effect of age-of-dam. This should be evaluated and considered when performing genetic evaluation analyses where multiple breeds are included. | It has been observed that some breeders preferentially treat different age of dams differently resulting in a contemporary group by age of dam interaction on some traits where there is a main effect of age-of-dam. This should be evaluated and considered when performing genetic evaluation analyses where multiple breeds are included. | ||
Also, when evaluating age-of-dam effects it should be remembered that culling and selection will occur as cows age. This can result in culling and selection [[Prediction Bias | bias]] in the estimates of age-of-dam effects. | |||
=Age-of-Dam Categories= | =Age-of-Dam Categories= | ||
Revision as of 04:04, 6 January 2020
Traits affected by a maternal contribution have the potential to have an effect that results from the age of the dam. BIF has identified the following categories as a standard classification for fixed age-of-dam effects in prediction models. The categories are also used in determining adjustment factors for some traits.
It is clear that the age-of-dam effect can be different in different breeds. This is likely to be mostly due to the effect of scaling. If adjusting weights or measures for age-of-dam, different breed or size/scaling effects should be considered.
It has been observed that some breeders preferentially treat different age of dams differently resulting in a contemporary group by age of dam interaction on some traits where there is a main effect of age-of-dam. This should be evaluated and considered when performing genetic evaluation analyses where multiple breeds are included.
Also, when evaluating age-of-dam effects it should be remembered that culling and selection will occur as cows age. This can result in culling and selection bias in the estimates of age-of-dam effects.
Age-of-Dam Categories
Age in days for age-of-dam categories (years of age).
| Age-Of-Dam Classification | |||
|---|---|---|---|
| AOD | Low | High | # of Days |
| 2 | 639 | 1003 | 365 |
| 3 | 1004 | 1369 | 366 |
| 4 | 1370 | 1734 | 365 |
| 5 through 9 | 1735 | 3560 | 1826 |
| 10 | 3561 | 3925 | 365 |
| 11 | 3926 | 4291 | 366 |
| 12 | 4292 | 4656 | 365 |
| 13+ | 4657 |
