Breeder profile Mathieu ROUX (73)14 June 2020
Progress in genetics with Tarins embryos1 January 2023
The first Single Step indexation for dairy breeds provides an opportunity to take stock of this new development. Developed by French and international geneticists, it enables indexes to be calculated in a single step, harmonized internationally, corrected for genetic progress, and better integration of all genotyping data.
What is indexing?
Indexing is the calculation of an animal’s genetic potential. The principle is to solve an equation:
Performance = environment + genetics
Until the penultimate indexing, indexes were calculated in two stages. The first stage, called “sire confirmation”, is based on the performance of his daughters, and results in the publication of polygenic indexes. The second stage integrates genotyping data.
Why the single step?
The democratization and expansion of genotyping over the past decade has introduced a bias into this model. More and more animals are being genotyped all over the world:
- Or as part of selection schemes to pre-select AI sires.
- Or with your breeders, to select females and work only on those that meet your objectives.
However, this pre-selection is not taken into account in polygenic indexing, and thus “forgets” more and more information about the animals. Thus, with the single step, and thanks to advances in computer technology, genotyping data are integrated from the outset, enabling a more realistic representation of both the reference population and actual genetic progress. This correction of the pre-selection bias therefore leads to an increase in genetic progress, and highlights the fact that over the last 10 years, genetic progress has been underestimated, to a greater or lesser extent depending on the size of the breeds evaluated and the date of arrival of genomics within these breeds. In Abondance, the pre-selection bias was not very high, as genomic selection has only been possible since 2016.
What does this mean for Abundance and Tarin?
1. Correcting for the bias means higher index levels for young animals, which in turn means higher selection thresholds. Our latest series of sires in the Tarine breed have gained an average of +2 pts in UIS and in the Abondance breed have gained an average of +6 pts in UIS.
2. For the Tarine breed, a reclassification of only 2% (up or down) for males, and 8% for genotyped females. For the Abondance breed, only 3% of males have been reclassified (upwards or downwards), and 12% for genotyped females. The female population also shows a better distribution in index classes, with the appearance of more extreme animals.
Average ISU evolution Abondance male breed
Change in average ISU for Tarine males
3. A Birth/Calving index available for genotyped animals. At last, we’ll be able to say whether a young bull can be used on heifers or not.
4. A slight gain in precision: even if the aim of the Single Step is to gain in consistency, with the concomitant evolutions of this model, such as the harmonization of CD calculation for all traits, we were able to observe an increase in CD on young animals:
Tarine breed CD
What's in it for us?
Single Step is a reliable method that has been tried and tested in several studies, providing more information for genotyped animals and ever greater quality in genetic predictions and future field results.
The calculation method may have changed, but the services we provide to breeders have not, and our determination to support you as closely as possible in meeting your needs is all the stronger for it!