FAQ Indexrun April 2018

GES (Genetische Evaluatie Stieren) has revised and improved the estimated breeding value system. A number of changes will be implemented in the index run of April 2018. This ‘Questions & Answers’ provides the answers to many FAQs, presented in clear categories. Is the answer you need missing? Please contact your area manager.

REFERENCE POPULATION

What is a reference population?

A genomic test means nothing on its own. This test is only relevant if the markers of a particular animal are linked to traits. To do this, the daughter breeding values (without DNA information) of a large group of bulls (and now female animals too) are compared with their markers. This group is referred to as the ‘reference population’. The larger the reference population, the more reliable and accurate the genomic breeding values are. To ensure a large reference population for Holstein, CRV collaborates with other European cattle improvement organisations under the name EuroGenomics. The European reference population for Holstein currently numbers some 35,000 bulls.

Figure 1 In the new situation young sires will be better estimated and their ranking might change one

What will change in the reference population?

Genomic breeding values are calculated based on a reference population. Until now, this reference population consisted of the data of 35,000 bulls, made available thanks to collaboration between CRV and various partners in the  EuroGenomics project. Data collected from around 100,000 Dutch and Flemisch cows from FokkerijDataPlus (BreedingDataPlus) and Fokken op Maat (Customised Breeding) was recently added to this reference population. This has improved the genomic breeding values: we can now link the markers even more accurately to specific traits of the animals. The actual genetic value of cows and bulls can be estimated more reliably, and the stability of the breeding values is increased. This is a fantastic result achieved through cooperation between CRV and cattle farmers – a result we can all benefit from.

Will we notice the effects of a larger reference population in practice? 

The increased reliability means slightly a larger distribution will be seen in the breeding values. The genetically superior animals will achieve higher scores more easily while the genetically inferior animals will show clearly lower scores. Due to these changes in the reference population, the breeding values of young bulls, and their ranking, may change once. On the other hand, the marker breeding values will be more stable and give a more reliable estimation of the actual genetic value.

What does the larger reference population signify for individual (genomic) breeding values?

The larger reference population improves the genomic breeding value estimation. This will increase the reliability of some genomic breeding values. For example:

  • the reliability of the breeding value for milk will increase by 8% to 80%;
  • the reliability of the breeding value for conformation traits for udders and legs will increase by 4% and 3% to reach 74% and 61% respectively.

In addition, the genomic breeding values for udder health and fertility can also be estimated more accurately. With a reliability of more than 60%, the values are comparable to a breeding value of a third calf cow without a genomic test.

LONGEVITY

Will the longevity breeding value be affected?

The breeding value for longevity will be calculated in a different, better way from April:

  • The progression of the longevity breeding value differs for each bull. The factors that determine culling, and therefore longevity, change throughout the course of the bull’s life. The reasons for culling a heifer (production, milk let-down etc.) are often different for an older cow (udder health, fertility etc.).
  • In addition, additional predictors for the longevity of young bulls, such as sub-clinical mastitis, claw health and locomotion, also contribute to improving the breeding value.
What does the new calculation mean for the longevity breeding value? 

GES will not change how the breeding value for longevity is presented. GES will also express the new longevity breeding value in days and the spread will be identical to the old model. The reliability of the longevity breeding value for young bulls will increase (5-10%) and fluctuate less. The estimation for bulls will be much more accurate!

Figure 2 The new model will ensure that the breeding value for longevity (genetic – new) more closely approximates the actual longevity performance (phenotypic trend)

Will the new calculation method of longevity affect CRV bulls?

The breeding value for longevity will be calculated differently, but more reliably. The bull ranking will change once, but for the majority of bulls any changes to the longevity breeding value will be limited.

A limited number of bulls will see a change in longevity of more than 300 days. One of these is Stellando, whose breeding value for longevity will drop in April. The old model over-estimated his longevity value as very few animals were culled
in the first and second lactation. The current model takes the variation in culling (reasons) in various lactations into account. The revised method of calculating the longevity breeding value approximates what happens in practice better. The
situations in practice show that, despite strong first lactations, Stellando daughters tend to be culled more quickly afterwards.

Rocky is an example of a bull who is already a daughter proven top bull for longevity. In the new calculation model, taking the progression of his own longevity into account, the figures can be estimated more accurately and indicate he will transmit longevity of more than 1,000 days.

Figure 3 In the previous calculation sire A and B had a similar longevity breeding value. Now the course of longevity in a lifetime is taken into account of the individual sires and the longevity breeding value will be better estimated

Will the longevity breeding value for young top bulls change?

The values for young top bulls are now estimated more accurately. Combined with the fact that CRV focusses on bulls with good longevity, this means an increase in the number of bulls will longevity of more than 1,000 days.

Can we really expect daughters of these bulls to perform for more than 500 days on the farm?

Definitely. Longevity is genetically determined and cows already have the genetic capacity to perform for longer. However, market conditions and personal choices mean these animals are often withheld the chance to fulfil their potential. Experiences in the past after similar market conditions have shown that longevity quickly rises again. We expect that the age at culling is set to rise by at least six months in the coming years.

Moreover, we already have daughter proven bulls who transmit longevity of more than 700 days. So it is not surprising to expect the next generation of bulls to reach a longevity breeding value of 1,000 days or more, and produce daughters who can perform for at least 500 days. Rocky is an example of a bull who is already a daughter proven top bull for longevity. In the new model, taking his own curve into account, the figures can be estimated more accurately and indicate he will transmit longevity of more than 1,000 days.

Figure 4 Effect of bull breeding values for longevity on the realized productive life of daughters

If the longevity breeding value increases, why is this not reflected in the annual statistics? 

Despite cows having the genetic capacity to perform longer, we have not seen an increase in the age at culling in recent years. This is due to market conditions and personal choices. For example, phosphate legislation often prompted the culling of older cows so the percentage of new heifers joining the herd as a replacement increased. Experiences in the past after similar restrictive market conditions have shown that longevity quickly rises again. We expect that the age at culling is set to rise by at least six months in the coming years.

How does the survival score correlate to the breeding value for longevity?

The survival score indicates the percentage of daughters that are still part of the herd after a certain number of months. The survival score is a rough figure that is not only influenced by genetic predisposition but also by factors such as the
environment and chance. The survival score does not take culling in other lactations into account or how good the farms and cows are where the bull was used. The longevity breeding value is therefore a better indicator for individual bulls.

The longevity breeding value gives farmers the best possible estimation of the bull’s genetic capacity to increase herd longevity. This estimation is based on several valuable sources of information:

  • with a young bull: its genetic predisposition (genomics);
  • its parents’ breeding values;
  • bulls with daughters: corrected survival scores and daughter breeding values of traits that predict longevity

If we examine the breeding value longevity of all CRV bulls in the publications of the GES, we can also see a clear correlation between the breeding value longevity and the survival score.

NVI MILK

What changes are ahead in the formula of the Dutch/Flemish Index (NVI)?

A debate on the breeding goal is held about once every five years. The NVI for dairy breeds in the index run for April 2018 is a better fit with the breeding goals of Dutch and Flemish dairy farmers. Via open consultation (including during the winter meeting), no fewer than 4,000 Dutch and 1,200 Flemish herdbook members indicated which points they considered needed attention in the breeding goal. Points they mentioned included greater attention for efficiency, healthy claws and fertility but additionally maintaining sufficient attention for production traits. This has resulted in a positive change to the NVI formula which will be implemented by GES in April 2018.

Figure 5 Weighting in the new NVI for dairy breeds

For years, CRV’s aim has been a healthy herd with efficient lifetime production. As well as the revised NVI, farmers can also use the unique CRV breeding figures Better Life Health and Better Life Efficiency. Results in practice have demonstrated that breeding based on these indexes results in cows that efficiently convert feed into milk and produce easily and with no problems. Whereas the NVI is a national index, the Better Life indexes have been developed
by CRV. Farmers can use the Better Life indexes within the framework of their individual breeding goals or bull selection decisions.

Table 1 Weighting in the current and new NVI for dairy breeds

Will the reliability of the NVI change?

The reliability of the NVI will decrease marginally (-2%) with the addition of the new traits ‘Saved feed costs for maintenance’ and ‘Claw health’. These traits have slightly lower reliability, which in turn decreases the average reliability a little.

NVI DUAL-PURPOSE

Will there be a new NVI for dual-purpose breeds? 

Yes. A specific NVI for dual-purpose breeds will be introduced with the April index. The Fleckvieh Herdbook, the MRIJ committee and the Blaarkop Association, who will form the dual-purpose council in the future, are the initiators behind this
development. The dual-purpose NVI is much more suitable for the breeding goals of farmers who use Fleckvieh, MRIJ or the typical Blaarkop breeds. There is greater emphasis in this specific NVI on the udder and beef traits that lead to higher turnover and growth.

Figure 6 Weighting in NVI for dual-purpose

Which breeds are considered to be dual-purpose?

The dual-purpose NVI can be used for Fleckvieh, MRIJ, Blaarkop and Friesian Black Pied cattle. Montbéliarde is included with dairy breeds.

What will change in the general characteristics for dual-purpose breeds? 

As well as a specific dual-purpose NVI, the general characteristics for these breeds will be amended:

  • In ‘Frame’ stature will have a higher weighting and rump structure will be given less priority;
  • In ‘Type’ the addition of muscularity and an optimal score for chest width and body depth for the dualpurpose type cow;
  • More influence for front and rear teat placement in ‘Udder’;
  • Identical weighting for rear and side view of legs in ‘Legs’.

GENERAL

The breeding value and/or ranking of bulls may be subject to change. Will this affect the SireMatch advice? 

Despite the breeding values and/or ranking of individual bulls being subject to change, the average level of bulls in a bull package will not deviate much. Any changes at herd level will therefore be limited. Having a clear breeding goal is the foundation for sound advice on the right bull, so do not make a preselection of bulls, but leave all the work to SireMatch.

Do the changes to the next index run only apply for CRV?

The changes to the next breeding value estimation will be implemented by the Genetic Evaluation Sires (GES). The key task of the GES is publishing reliable breeding values for bulls in the Netherlands and Flanders. CRV, in addition to other bull owners, is one of the participants in the GES foundation. The changes implemented by the GES in April therefore apply for all participants.

As well as the official GES breeding values, CRV also develops and publishes unique traits such as the Better Life breeding values. Nothing will change in relation to these breeding value estimations.