The
National Sheep Improvement Program is a computerized,
performance-based program for genetic selection. NSIP is designed
to help purebred sheep producers identify the best genetic stock
for their breeding programs. An Estimated Breeding Value (EBV)
is an estimate of an animal’s true breeding value. EBVs are
benchmarked, so they allow the animal to be fairly and directly
compared to the benchmark, the current breed average, or with other
animals from the same analysis. EBVs do not necessarily reflect the
animal’s observed performance, which is a combination of both
genetic and environmental influences; rather they are an estimate
of the genetic component of that performance.
Quick facts
about EBVs:
•
An EBV is a value (number) that expresses the difference (+ or –)
between an individual animal and the benchmark to which the animal
is being compared. An EBV of +6 for post-weaning weight means that
the animal is genetically better by 6 kg at post-weaning age than
the base it is being compared to. EBVs are reported in terms of
actual product, for example kg of weight, mm of fat depth, or % of
lambs or kids weaned.
•
EBVs adjust for known environmental differences such as age, age of
dam, birth type, rear type and nutrition. This allows comparison of
animals born in different seasons and years, and adjusts for known
genetic differences such as preferential joining and unequal
representation between contemporary groups.
•
EBVs consider all the available information from relatives as well
as the individual animal, and take account of the relationship
(correlation) between traits.
•
An EBV is the best estimate of genetic merit. The value of an
animal’s genes for most production traits cannot be directly
measured. This means that, given all the data available, the
estimate is unbiased and as close to the true value of the genes as
we can get. However, practically we cannot determine an animal’s
true genetic value so we must settle for the best estimate. An EBV
will never have an accuracy of 100% but as very well evaluated
animals (sires with many recorded progeny, for example) get EBVs
approaching 99% accuracy, the estimate is very close to the animals
true breeding value.
This information can
be found at the NSIP website: http://nsip.org/
