24
mars
2021

From April 2021, the RZG includes new breeding values and findings

From April 2021, the RZG includes new breeding values and findings

Germany is an international leader when it comes to quality of breeding value estimation for dairy cattle. This is true for both the total merit index RZG and the estimation of single breeding values. In co-operation with the data center vit, German breeding organizations and farmers, the further development of the breeding value estimation has been very successful in the past few years. Through the co-operation of those different entities, the applied estimation methods are very practice-orientated and offer a reliable and secure data base.
With focus on healthy animals known for longevity, not only estimation methods have been improved over decades, but also traits in the field of health have been complemented. After the last adaption of the total merit index RZG in April 2008, there will be a new adapted RZG available from April 2021, combining all requirements of modern dairy cattle breeding.

With the recent rebalancing of the total merit index, the health breeding values RZhealth and RZcalfhealth are incorporated in the RZG now. With increasing weighting of the health traits, milk production may lose in weighting, but – according to the great economic importance – the RZM as milk production index will still have the highest weighting in the RZG with 36 %.
The RZhealth will be considered with 18 % in the new RZG due to its higher economic and social importance. In the past, the RZS served as supporting trait to improve udder health. The new RZudderfit, a partial breeding value of the RZhealth, is a more precise parameter for which reason the RZS will not be taken into account in the new RZG. However, there will be breeding progress in cell score via positive correlation with the RZudderfit.
RZN and RZR will also be influenced indirectly in a positive way by the RZhealth. Due to this, those traits’ weighting will be lower resulting in RZN 18 % and RZR 7 % in the new RZG.
The breeding value for losses during rearing in calves will also be new in the RZG. The new RZG includes the RZcalfhealth with 3 %. Moreover, calving traits will have a weighting of 3 % (1.5 % RZKd and 1.5 % RZKm) in the new RZG.

Because of its high importance and close correlation to longevity, so far only feet & legs and udder were considered in the RZG. Regarding conformation, the trait complex “body” will be part of the RZG in future besides feet & legs and udder. Therefore, rump angle, rump width and strength as important body traits will be brought further in the focus. The conformation traits will be part of the RZG with 15 %, in relation to 45 % udder, 35 % feet & legs, 20 % body. On the one hand, conformation just has lower economic importance, but on the other hand there are quite positive effects due to better functionality when considering good conformation breeding values.

The new RZG will be introduced with the new April 2021 breeding value estimation and will then be available for all bulls as well as genotyped female animals. A total merit index that absolutely lives up to expectations and the breeding goal of German Holsteins.

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