Page 10 - Merchiston Angus Catalogue ebook

INDEX DESCRIPTIONS Angus Pure Index (API)

New Zealand Angus AngusPure Index - Predicted Response
The following three graphs reflects the relative change if the
New Zealand Angus Published Sires (at the Mid-August 2020
TransTasman Angus Cattle Evaluation) were ranked on this
selection index and the top 10% were used within a breeding
program. Given that the Published Sires are the sires of the Expected Change in Individual Traits
next generation(s) of New Zealand Angus cattle and have
more highly accurate EBVs (due to having progeny) than the
average animal in the database, these graphs represent the
approximate selection response one would expect to see in the
breed from using this index. CEd CEm GL BW 200W 400W 600W MCW Milk SS DC Cwt EMA Rib Rump RBY IMF

Above the 0 line (X axis) selects for more positive numbers and below
Self Replacing Index (SRI) the line selects for more negative numbers. For some traits
(e.g. growth), a positive response is desirable and for others
New Zealand Angus Self-Replacing Index - Predicted Response Genetic Selection of bulls using only the API tool will on
(e.g. days to calving), a negative response is desirable.
Expected Change in Individual Traits average over time develop a cow herd with the following:

•
Improved weaning rate through increased fertility and
easier calving
•
Progeny will be prime at heavy carcase weights where the
• A slowly increasing cow weight/size, and milk production
CEd CEm GL BW 200W 400W 600W MCW Milk SS DC Cwt EMA Rib Rump RBY IMF improved marbling and subsequent eating quality traits
can be expressed

Above the 0 line (X axis) selects for more positive numbers and below
the line selects for more negative numbers. For some traits These characteristics are ideal for an environment where the
(e.g. growth), a positive response is desirable and for others
(e.g. days to calving), a negative response is desirable. cow herd can be managed with extra feed if seasonal feed
deficits occur.

Genetic Selection of bulls using only the SRI tool will on
average over time develop a cow herd with the following: Checking individual EBVs relevant to your herd is advised.
• Improved weaning rate through increased fertility and
easier calving Comparison of SRI and API
• A slowly decreasing cow size, milk and slowly increasing SRI is a maternal trait emphasised index. API is also a maternal
body condition driven index with added carcase trait emphasis.
• Progeny will be prime at a younger age for slaughter
API selected animals can produce more net profit per animal
These characteristics are ideal for an environment where through extra performance when feed is abundant.
the herd is exposed to prolonged seasonal feed deficits and Finished progeny can be taken to heavier weights with
feeding supplement is unlikely. increased likelihood of achieving marbling premiums.

SRI selected animals can produce more net profit per animal
Checking individual EBV’s relevant to your herd is advised. through extra performance in environments where
the cow herd is likely to be challenged by regular seasonal feed
deficits, maintaining body condition is critical
to longevity and feeding out is not a viable option.

Checking individual bull EBVs to make sure the index
and the EBVs match your expectations are advised.
Using the flow chart may help you with your decisions.
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