New proofs 2022 - New ISU & new calculation method

New proofs 2022 - New ISU & new calculation method

Le 12/04/2022


Revision of the Montbeliarde ISU
The last revision of the ISU index was in 2012. A reform of a breed’s selection index was necessary for the selection objectives to correspond to the economic conditions of the Montbeliarde herds, the genetic progress of the breed, and to integrate new traits available. The new ISU has been created by Montbeliarde Association in partnership with the selection companies and IDELE support.

Major changes in the new ISU
> Affirm body condition and beef value of the Montbeliarde breed
> Give more weight to functional traits: longevity and udder health
> Rebalance the fat & protein % in the production category
> Integrate selection for improved temperament


New genetic calculation method: the SINGLE STEP
Starting with the April 2022 proofs, a new calculation method called SINGLE STEP is used. It has been implemented broadly by all our partners: IDELE, GENEVAL, ALLICE and INRAE within the UNIGENO project and is used in the genetic estimation of all French breeds using genomic information. This method is also used internationally.

Why a new indexing method?
For several years, the percentage of genotyped animals have increased. Thanks to this tool, animals with poor performance predictions are culled before they go into production, both males and females. Thus, only the best animals are given an opportunity to contribute performance data, which leads to an overestimation
of the reference population (those animals with genomic testing + performance information) and an underestimation of the indexed animals (the whole population): this concept is called pre-selection bias.
The objective of the single step method is to correct this pre-selection bias by considering all the information available for all animals simultaneously, whether they enter production or not. With the single step, noticeable information increases, particularly in the evaluations of young animals, now corrected for the pre-selection bias.

SINGLE STEP, what are the main evolutions?
> Change from two steps to one: single step means all pedigree, performance, and genotype data are eva-luated simultaneously
> All genotypes are considered in the reference population
> A method that now fairly compares genotyped and non-genotyped animals
> Correction of the pre-selection bias