Page 10 - Woodbank-Matariki ebook

ANGUS INDEXES EXPLAINED AngusPure Index (API)

New Zealand Angus AngusPure Index - Predicted Response
INDEX DESCRIPTIONS
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 next Expected Change in Individual Traits
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
Self Replacing Index (SRI) Above the 0 line (X axis) selects for more positive numbers and below
the line selects for more negative numbers. For some traits (e.g. growth),

a positive response is desirable and for others (e.g. days to calving),
New Zealand Angus Self-Replacing Index - Predicted Response a negative response is desirable.
Genetic Selection of bulls using only the API tool will on
Expected Change in Individual Traits • Improved weaning rate through increased fertility
average over time develop a cow herd with the following:

and easier calving
• A slowly increasing cow weight/size, and milk production
• Progeny will be prime at heavy carcase weights where the
improved marbling and subsequent eating quality traits
can be expressed.
These characteristics are ideal for an environment where
CEd CEm GL BW 200W 400W 600W MCW Milk SS DC Cwt EMA Rib Rump RBY IMF the cow herd can be managed with extra feed if seasonal feed
deficits occur.
Above the 0 line (X axis) selects for more positive numbers and below
the line selects for more negative numbers. For some traits (e.g. growth), Comparison of SRI and API
a positive response is desirable and for others (e.g. days to calving),
a negative response is desirable. SRI is a maternal trait emphasised index. API is also a maternal
driven index with added carcase trait emphasis.
Genetic Selection of bulls using only the SRI tool will on
average over time develop a cow herd with the following: API selected animals can produce more net profit per animal
through extra performance when feed is abundant.
• Improved weaning rate through increased fertility Finished progeny can be taken to heavier weights with increased
and easier calving likelihood of achieving marbling premiums.
• A slowly decreasing cow size, milk and slowly increasing
body condition SRI selected animals can produce more net profit per animal
through extra performance in environments where
• Progeny will be prime at a younger age for slaughter
the cow herd is likely to be challenged by regular seasonal feed
These characteristics are ideal for an environment where the herd deficits, maintaining body condition is critical
is exposed to prolonged seasonal feed deficits and feeding to longevity and feeding out is not a viable option.
supplement is unlikely.

8 Woodbank Angus & Matariki Herefords Bull Sale 2021