Breeding value estimation
Vereinigte Informationssysteme Tierhaltung w.V. (vit)
The data centre Vereinigte Informationssysteme Tierhaltung w.V. (vit) collects centrally all data for the dairy cattle breeds. This central data base which, compared internationally, is unique in terms of size and quality, acts as an independent institution carrying out the nationwide, state-controlled breeding value estimation for the Holstein, Red Holstein, Angler, Red and White dual purpose (DN) and Jersey breeds as well as German Friesian cattle (DSN). The list of breeding values contains all the economically important traits from milk production to milking speed. The statistic models used are among the best in the world.
Milk production and udder health
Since 1997, breeding values for milk production and somatic cell score have been estimated directly on the basis of daily yields measured monthly on the farms using a test day model. Therefore a summary or expansion for lactation yields is not carried out. Correction for all non-genetic effects is optimal because performance is compared within herd-test-day, i.e. the same environment and management. Measuring the cell count in every milk sample is standard in Germany. Therefore the data base for udder health is exactly the same as for milk yield and it is unique in the world.
Breeding value estimation for conformation contains all linear standard traits recommended by WHFF (World Holstein Friesian Federation) as well as, additionally, the trait “hock quality” for feet and legs. Moreover, using classifier information, breeding values are estimated for four composite scores: udder, feet and legs, body, dairy type. Within the RZE (relative breeding value conformation) as well as the four published composite figures, information from the linear traits and classifiers scores are all combined. The selection of test bull daughters and comparative daughters to be classified is done centrally by the VIT within all herds under official milk recording. Breeding values for conformation are based on the entire breadth of the population and, therefore, not for example, only on the basis of selected herd book herds.
For the evaluation of productive life, a culling risk model is implemented (Survival Kit). This not only accounts for culled cows with their definite productive life, but also live animals with their current productive life. Productive life is corrected for the different treatment owners give to high or low yielding cows within a herd (functional productive life). Because of limited data on productive life for younger bulls, the reliability of the RZN (relative breeding value longevity) is improved by using information of the supporting traits cell score, udder depth, feet and legs, capacity and daughter calving ability.
Total Merit Index RZG
The total merit index RZG, includes all important traits according to their economic importance. In 1997, Germany was one of the first countries to have a real total merit index with production, conformation and functional traits like longevity and fertility. Since the last adjustment in April 2008, the functional traits have been weighted at 40 %, conformation 15 % and production at 45 %.
Fertility of high performing cows is complex. Therefore breeding values are estimated for five different traits from the complexes “re-cycling after calving” and “conception ability”. The five breeding values are summarized in the RZR (relative breeding value reproduction) according to their economic significance. The data base includes all inseminations of all cows and young cattle in all herds under official milk recording.
Calving traits always include two aspects: the direct calf effect (e.g. size of the calf) and the effect of the dam (e.g. dam’s form of rump). Both aspects have the same impact on trouble-free calving. As there are two information traits, calving ease and vitality of calves (still birth rate), there are 4 single breeding values. Direct calving ease and direct still birth rate are summarized in the relative breeding value, direct calving ease (RZKd), describing the calving ease of a bull’s calves. The two maternal breeding values, maternal calving ease and maternal still birth rate, are summarized in the relative breeding value maternal calving ease (RZKm), describing the calving traits of a bull’s daughters.
More functional traits
In addition to the above-mentioned traits included in the total merit index, breeding values for more traits are available:
• Milking speed (based on measured milk flow and owner’s scores)
• Milking temperament (owner’s scores)
• Persistency (from lactation curves)
• Body condition score
Furthermore, fertilization ability of the semen of a bull is reported as % of the non-return rate.
Relative breeding values
All breeding values – except milk production traits – and summarizing indices are published as relative breeding values. Thus the figures are directly comparable across traits and the higher value always indicates the more desirable breeding performance. The scale for all relative breeding values uses 100 as average and a genetic standard deviation of 12 points.
Since August 2009, VIT has been evaluating a combined fitness index. Using the new RZFit, it is possible to easily find the bulls with the best fitness traits among the very high number of proven Holstein bulls. German Holstein breeding offers bulls that transmit very positively in this composite and – with that – bring adequate improvement.
Daughter fertility and calving traits have the highest weighting in the RZFit with 20 % each, followed by longevity with 15 %. For maternal calving traits, calving ease and still birth rate are weighted the same. As most fitness traits and milk yield are genetically correlated negatively, the production traits are weighted with 10 % in the RZFit. This turned out to be a good solution.
Suitability for automatic milking systems
In August 2014, VIT released a new breeding index specifically for farms with automatic milking systems (AMS) in order to facilitate selection of particular bulls.
The RZRobot is built from the following traits: milking speed (≥ 94), somatic cell count, feet & legs, udder, rear teat placement (≤ 106) and teat length (≥ 94). These six traits have different weightings within the RZRobot. For the traits milking speed, rear teat placement and teat length, minimum requirements were defined which are shown in brackets.
Furthermore, it has been decided, that the RZRobot will only be published if it is ≥ 100, to make sure the bulls will really improve the suitability for AMS.
Genomic breeding values
Since August 2010, genomic breeding values for Holsteins (Black & White and Red & White) have been official in Germany. In fact, they are among the most reliable genomic breeding values worldwide because they are based on the EuroGenomics training sample (reference population), containing more than 28,000 reliable daughter proven and, at the same time, genotyped bulls, of which approx. 11,000 bulls have daughters in Germany. The quality and unbiased nature of German genomic breeding values, which are very high, is not only confirmed by ICAR/Interbull validation, but also by almost 2,000 bulls, that previously only had genomic breeding values, and now have classical breeding values based on more than 100 daughters to date.
Information on genomic selection can be obtained at www.ggi.de – Holstein breeding – Genomic selection.
Please do not hesitate to contact us in case you have any further questions.