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We do something similar to that with our NZ herd! We never cull for age,
only mainly SCC, late or empty, milk production lower than a heifer that
would replace her. Any cows with continuous lameness issues go to our
smaller farm with better races and less walking distances, and they usually
do well there too. So we have about 10-20% of our herd over 9 years old,
and we breed them to AI and keep all their heifer calves. I know of many
cows that got to around 14 years old and conceived to their first mating
every year. And if you look at their daughters they all remain in the herd
for a long time too. So obviously fertility and longevity are heritable.
We have sometimes kept empty cows if they are our best producers, they take
a year off then get in calf again and produce. But we have noticed that it
wont take long before they are empty again, and if we have any daughters
from them, they tend to become empty or have conception problems as well.
Michelle.
On 7/1/06, F. W. Owen <fwo@bright.net> wrote:
>
> > If fertility is 5% inheritable and other traits in the herd such as
> udders
> > and production are 45% inheritable, wouldn't it be more profitable to
> > concentrate on the higher heritability traits until they are
> satisfactory
> > before addressing something that is only 5% inheritable? Keep in mind
> > that the more traits you select for, the slower the genetic
improvement
> in
> > each trait.
>
> Well, there was once and still is a whole different approach now in
> disfavor.
>
> We could just refrain from concern over such factors as % heritability and
> generation interval, and instead raise bulls only from 10 year old and
> older
> cows with regular breeding intervals.
>
> The assumption being that if the cows withstood 10 years of culling, and
> attrition from natural causes, then such cows may be genetically superior.
>
> --
> Kindest regards,
>
> ========================
> F. W. Owen
> Owenlea Holsteins
> 9430 Spencer Road
> Homerville, Ohio 44235
> e-mail fwo@bright.net
> home page http://www.bright.net/~fwo
> voice & fax 330.625.2369
> cell 330.635.2287
> ========================
>
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