Wednesday, 3 February 2016

More accurate hoof health breeding values

By Emma Carlén, Anders Fogh and Terhi Vahlsten (NAV/Växa/Seges/Faba) 

The most important change when a new hoof health genetic evaluation was introduced in NAV in November 2015 is that the reliability of hoof health breeding values for especially cows are markedly improved.

The main reason for this is that published cow breeding values are now based also on their own hoof recordings and not only on pedigree information which was the case previously. Other improvements in the evaluation are updated genetic parameters and a new method for reliability calculation. The latter implies that reliabilities for bulls drop slightly compared to previously. Also data quality and editing have been improved.

Higher reliability for genomic animals
One ongoing process in NAV is to change evaluation for all trait groups to models where the breeding values for cows also include own performance. Cows can then be in the reference population behind the genomic breeding values. In this way it is compensated for the testing fewer bulls in future
                      For hoof health the development work with including cows in the reference population has not yet been made. This will be at a later stage.

EBV for hoof health can change
This new information and the increased reliability in cow breeding values for hoof health imply that cow breeding values change more than usual. The correlation between hoof health index EBVs for cows in August 2015 and in November 2015 is around 0.85 while the corresponding figure for bulls is around 0.95 - slightly lower for Jersey.

Leading in hoof health
The Nordic countries, have been pioneers on registration and genetic evaluation of hoof health. The breeding value evaluation today includes seven different hoof disorders recorded in the first three lactations. Traditional breeding values (EBV) based on registration from hoof trimmers was introduced in Sweden already in 2006 and in NAV in 2011. Last year  genomically enhanced breeding values (GEBV) were included 

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