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An Evaluation of High Genetic Merit Cows Using Forage and Pasture-based Systems.
Dillon, Pat Buckley, Frank
Dillon, Pat
Buckley, Frank
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1999-09-01
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Dillon, P., Buckley, F., An Evaluation of High Genetic Merit Cows Using Forage and Pasture-based Systems, End of Project Reports, Teagasc, 1999.
Abstract
The rate of genetic improvement in Ireland up until the mid-80’s was
low (approx. 0.5% per year) compared to North America where genetic
merit for milk production was increasing by 1.5% per year (Funk,
1993). Since 1985 the rate of genetic improvement increased
markedly to about 1.5% per year in 1992 (Coffey, 1992). This high
rate of genetic progress has mostly been achieved through the
importation of North American and European genetics. The relative
merit of these sires has been obtained from the performance of their
progeny in systems of milk production which differ greatly from those
operated in Ireland.
The term “high genetic index” (HGI) is used to describe a cow, which
as a result of selection, is generally predisposed to produce
significantly more milk than a cow of lower merit status. Studies
from New Zealand have shown that cows of high “genetic index” at
pasture, produce more milk (20 to 40%), consume more herbage (5
to 20%), were more efficient convertors of food into milk (10 to 15%)
than lower merit cows (Holmes, 1988). However, these “high”
genetic index cows would be considered “low” when compared to
present-day genetics. Recent results from Langhill (Veerkamp et al.,
1994) have shown that increasing genetic index results in major
increases in feed efficiency, reflecting increases in milk yield with
cows fed indoors on silage/concentrate diets. There is little
information available on the performance of present-day HGI dairy
cows, on seasonal calving, grass-based systems of milk production