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 Holstein, Red Holstein, Angler, Red and White dual purpose (DN) and Jersey breeds as well as German Friesian cattle (DSN). 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 these breeds. 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.
Detailed information on evaluation models, data and trait definitions can be obtained at www.vit.de.
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.
The breeding value for longevity (RZN) has been published based on nine survival breeding values since April. These survival breeding values themselves represent nine phases of life. From first to fourth calving, the 3 lactations resulting from them are divided in three phases. So first, real survival information will be already available on the 50th day of the first lactation marking the end of the first phase. So all bulls will get – at the same time – longevity breeding values based on daughter information with the first daughter proven breeding values for milk production/cell score. In line with other relative breeding values, a RZN for A.I. bulls is published if daughter information (1st phase 1st lactation) is based on at least 10 farms.
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. Regarding the composition of the RZG, the functional traits are weighted at 40 %, conformation at 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
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 had calculated and published a summarizing fitness index, the RZFit. The RZFit included the traits daughter fertility (RZR), maternal calving ease (RZKm), feet and legs, longevity (RZN), udder health, udder and milk production (RZM) which were clearly weighted in favor of the functional traits. These traits have in common that they describe aspects that allow conclusion of good fitness. In April 2019, the RZFit will be replaced by the newly developed RZhealth that includes traits that allow direct conclusion of health/fitness.
From April 2019, the new breeding value RZhealth will be published for every bull. It consists of the four complex breeding values RZudderfit, RZhoof, RZrepro and RZmetabol. RZEuter has the highest weighting here with 40 % as a relatively high percentage of cows at least contracts Mastitis once in their lifetime and costs per each Mastitis case are high. The second most important complex is hoof health which is why the RZhoof is weighted with 30 %. RZrepro is weighted with 20 % and the complex on metabolic persistency, the RZmetabol, has a weighting of 10 %. The four complex breeding values themselves consist of differently weighted single traits which can be seen in the table below.
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 and established in Germany. The previous, pure sire reference sample is set up by the EuroGenomics reference sample and includes more than 35,000 reliably daughter proven and, at the same time, genotyped bulls, thereof approx. 13,000 with daughters in Germany.
In line with the breeding value estimation in April 2019, the pure sire reference sample is changed to a mixed reference sample then including more than 38,000 bulls and 150,000 cows. 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.