21 January 2013

Sire Trait Leaders

This article was prompted by members' responses to the article on Breedplan. Although often referred to by stud breeders and in official literature, no current definition of what constitutes a Limousin trait leader in Australia and New Zealand could be found in official publications.

However, a review of published sire lists available on the ABRI website enabled selection criteria to be deduced, although the criteria do seem to change over relatively short periods. This review is valid for the January 2013 listing.

For a sire to become a trait leader it must satisfy three criteria. Firstly, the sire must be a published sire. Secondly, the sire must have an EBV accuracy in one of 13 selected traits of 75% or greater. Finally, the EBV must be ranked in the top 5%, 10% or 20% of the breed, depending upon the trait, when compared with calves born in the reference year (currently 2011). Percentile bands for 2011 born calves can be found on the ABRI website.

Published Sires

A list of published sires can be generated by visiting the Animal Search page on the ABRI website, and selecting Animal is a Published Sire in the Select if: box. The January 2013 list of published Limousin sires comprises 305 sires. The criteria for these published sires appears to be:

The selection criteria appear to change from time to time. In June 2012, the Limousin listing include two Angus sires!! The list published in the last Sire Summary (2011) comprised several sires with all growth trait EBV accuracies well below 75%, but at least one other trait with an accuracy greater than 75%.

Trait Leader Criteria

Of the 305 published Limousin sires, 139 had at least one trait that satisfied the trait leader criteria. Trait leader EBVs are identified by a blue cell.

As with the published sire list, the criteria for trait leaders also appears to change. In June 2012, two Angus appearing in the Limousin list were recorded as trait leaders for gestation length and scrotal size. The list also identified trait leaders for mature cow weight (oddly heavier was considered better). Earlier lists identified birthweight trait leaders, which is no longer listed. Trait leaders were not identified for docility in earlier lists but are now.

Criteria for trait leaders have also changed a number of times over the past two years. EBV accuracy requirements dropped to 60% or 65% for some traits (calving ease, EMA and rib fat). The minimum accuracy requirement to be trait leader no seems to have stabilised at 75%.

Next, the EBV must achieve or exceed a trait-dependent minimum ranking relative to calves born in the reference year (currently 2011). Of the 17 traits for which EBVs are published, 13 are assessed for trait leaders. These are listed below with their ranking and trait accuracy requirement.

Calv
Ease
DIR
Calv
Ease
DTRS
Gestn
Len
200
Day
Wt
400
Day
Wt
600
Day
Wt
Milk Scrot
Size
Carc
Wt
Eye
Musc
Area
Rib
Fat
Ret
Beef
Yield
Doc
Minimum
Accuracy
75% 75% 75% 75% 75% 75% 75% 75% 75% 75% 75% 75% 75%
Minimum
Ranking
(Top %)
20% 20% 10% 5% 5% 5% 10% 10% 5% 20% 20% 20% 10%
Number of Sires
Satisfying Trait
Leader Criteria
21 15 33 39 42 41 18 40 20 6 8 4 47

It is unclear who determines the trait leader criteria and why the criteria are not published. The distribution of trait leaders among the traits is also odd, ranging from a total of four (all imported genetics) for retail beef yield to 47 for docility.

Minor discrepancies exist in the number of sires satisfying the trait leader criteria, presumably because of rounding errors introduced in the published EBVs.


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