Page 7 - Catalogue Omagh 2023 Final web file
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Estimated breeding values are INTERPRETATION
expressed in the units the traits eBVs and selection indexes are a
are measured, weight traits are in function of the population in which
kilograms, NLB in lambs per ewe they are calculated. In all cases they
lambing. are comparable within a single flock.
Indexes: An index provides a For every analysis SIL sets 1995
summary of overall economic as the benchmark year and the
breeding value of animals. The average genetic merit of lambs
economic value of each trait is born in 1995 is set to zero.
summed to give a total economic Therefore, gBVs are measures of
value of the ram’s genetics. The genetic merit for a ram compared
economic value of a trait depends to the 1995 average for that
on the production system, evaluation. If two flocks had
therefore a number of indexes different average genetic merit in
are used to describe different 1995 the gBVs would have to be
systems. For example, the New adjusted for the difference to make
Zealand Terminal Worth (NZTW) them comparable
index describes a system where
all progeny are slaughtered. The When selecting a ram that is high
New Zealand Maternal Worth genetic merit it is important to first
(NZMW) index describes a system select the flock the ram was bred
where ewe lambs are retained as in. The ram should rank highly
replacements for breeding with within that flock for the key traits
surplus lambs going to carcass you are interested in. Index values
production. provide the best guide to overall
genetic merit across traits.
Sub-indexes are sometimes
reported. These refer to the In summary, whichever flock you
economic value for traits of a decide to buy a ram from, be sure
particular type –e.g. Lamb Growth to select one that is highly ranked
vs. Wool vs. Reproduction vs. Meat by SIL. This will guarantee improved
Yield (carcass quality). genetic merit in your flock
compared to using rams selected
All SIL indexes are expressed as cents without an accurate assessment of
per ewe lambing genetic merit.
OMAGH ANNUAL RAM SALE - 7
