Analysis changes

LAMBPLAN and MERINOSELECT analysis update May 2013

The Sheep Genetics Technical committee has advised in favour of and implemented the following changes for an improved analysis. These changes were reviewed and endorsed by the Sheep Genetics Advisory committee prior to implementation. While these are not considered major changes to the analysis some flocks may be affected.

Reproduction analysis – implement additional management grouping

Currently the default grouping strategy for the reproduction traits is by flock, year, ewe age class (1, 2 and 3+), conception method and lambed at 1 year of age (0 or 1). However some flocks have different management groups of ewes lambing at the same time and historically we have not been able to capture this information. These additional groups are now being recognized within the analysis when identified by the breeder.

Reproduction analysis – Yearling data

The average fertility of yearling ewes is only 53%. This means the current service sire filtering which has a minimum requirement of 50% fertility is removing too many records. To accommodate this, the 50% minimum requirement has now been lowered to 20%. This will increase the amount of data that is used in the analysis and allow further insight to the variation that exists for yearling lambing performance.

Reproduction analysis – modified data filtering

Reproduction data is only used from flock / drops that pass certain data quality filters. The filters were historically based on the count of lambs born however it will now be based on the counts of ewes lambing. This is more appropriate as the number of lambs born is influenced by litter size, such that different thresholds were being applied across flocks and years. These fertility counts are also used to filter out failed service sires.

Update years for genetic group allocation in MERINOSELECT analysis

Animals with unknown pedigree are allocated to a genetic group. Flocks with sufficient data over time are allocated time based period groups to accommodate genetic trend in the base animals. The last period group currently spans over 10 years for 2001 to 2013. An additional time period group has been created from 2006 onwards. This group is now being used by approximately 65 flocks and results in improved genetic trends for most flocks.