Understanding

EBV Accuracy

How EBVs could change with the addition of information

We often get questions from members about why EBVs for individual animals change, especially for proven sires with high accuracy.

This article will explain that EBVs can change as new data is added and we get a better statistical estimation of the animal’s genetics. This can occur even for proven sires that already have hundreds of progeny records, when members submit very large data files with potentially hundreds of additional records.

The accuracy value of an EBV gives an indication of the EBV’s reliability, and the likely extent of its possible change as more information becomes available. EBVs are based on the available information at the time of the BREEDPLAN analysis. The information available changes constantly as new data is added.

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As more data becomes available on an animal (or its progeny, or relatives) then the accuracy of the animal’s EBVs for particular traits will increase. It is likely that the EBV will also change as data is added, because the EBVs are based on data, pedigree, and genomic analysis.

For example, a bull at two years of age might have EBVs based on his own performance and the performance of his siblings, parents, and other relatives. Even though these EBVs will be lower in accuracy, they are still the best available statistical information on the Bull’s genetic merit.

As the bull is used in breeding programs and his progeny are recorded, more information is available about his likely genetic merit. As a result, his EBVs may change, and the accuracies will increase as the EBV estimation for the bull improve.

The EBV accuracy for a trait is influenced by the heritability of traits, the genetic association with other traits and the performance data recorded for those traits. For low heritability traits, more data is required to achieve a similar accuracy to that of highly heritable traits.

Table 1 below shows the confidence range at different levels of accuracy for each EBV published by the Australian Wagyu Association. As the trait accuracy for each EBV increases, the confidence range reduces significantly, meaning we expect less future change in the EBV.

1 Statistically, there is a 68% chance that an animal’s true breeding value will be within 1 standard deviation of its EBV, and a 96% chance that it will be within two standard deviations of its EBV.

The confidence range for each trait describes the maximum likely change to EBVs at different accuracy levels. Statistically, there is a 68% chance that an animal’s true breeding value will be within one standard deviation of its EBV.

For example, a 600-Day Weight EBV with an accuracy of 90% will have a confidence range of ± 10.3 kg. If an animal’s EBV is +70 then, with the addition of further information (e.g. progeny or sibling records), the EBV would be expected to be within the range of +59.7 kg to +80.3 kg (i.e. 70 ± 10.3 kg) 68% of the time (highlighted aqua in table 1 - page 19).

Accuracies are expressed as percentages. The higher the percentage, the greater the chance that the EBV is a close estimate of the animal’s true genetic merit, and a smaller likelihood that the EBV will change as more information becomes available.

Back to our original question regarding EBV changes in very high accuracy animals, normally proven sires. In Wagyu, it is not unusual to have a hundred carcase progeny records for a sire. These sires can have EBV accuracies of 95% or higher for carcase traits. It is also not unusual for such a sire to have tens or hundreds of additional carcase progeny records added over time.

For high accuracy animals, it is important to note that even the EBVs of proven sires can still change slightly with the addition of significant volumes of carcase progeny data. For example, a sire with a Marble Score EBV of +2.0 at 99% accuracy, can still be expected change by ± 0.2 MS units, with a likely EBV range of +1.8 to +2.2 MS units. (highlighted yellow in table 1 - page 19)

The change in EBV for a proven sire is driven by significant new carcase data records being submitted. In Wagyu, we have sires with more than 500 carcase progeny recorded and their carcase numbers are still increasing. So we can observe very large numbers of carcases being added to BREEDPLAN and these will have an impact on the EBV calculation, even for high accuracy animals.

For low accuracy animals, even though an EBV with a low accuracy may change in the future, it is still the best statistical estimate of an animal’s genetic merit for that trait. Generally, as more information becomes available, an EBV is just as likely to increase as it is to decrease, within the accuracy confidence range. The accuracy level of an EBV provides you with an estimate of the statistical confidence in the EBV and should be considered alongside the EBV value itself.

EBV accuracy

An indication of how reliable EBVs are

An EBVs accuracy is an indication of how reliable an EBV is and is therefore an important component to consider when making selection decisions for your breeding program. Put simply, the higher the accuracy, the better.

As a breeder, every time you make a decision to breed two animals, you are making a genetic selection decision, you are selecting the genetics you are passing onto the next generation. The higher an animal’s EBV accuracy is, the more reliable and the more predictable the response to genetic selection is.

Although EBV’s can be calculated based on an animal’s own performance data and genomics alone, the accuracy of EBVs increases when this information is used in conjunction with data from relatives – especially progeny performance data.

The power of Progeny Testing – increasing EBV accuracy

It is expected that as progeny data is submitted to BREEDPLAN, EBVs of individual sires will change (increase or decrease, see article on page 18) but the accuracy of the breeding values can only increase, making EBVs more reliable for producers to base their breeding decisions on.

The rate at which EBV accuracies increase varies, depending on a number of factors including the heritability of the trait (the proportion of the trait that is determined by genetics), the number of progeny (or relatives) with data submitted, and the contemporary group structure under which this data is collected.

Statistically, the most useful information to increase EBV accuracy comes from progeny in large contemporary (management) groups containing progeny from other sire/s which also have their data collected and submitted. This allows the genetic analysis to compare the relative performance of progeny of different sires to each other and establish the genetic differences due to the sires.

In cases where small amounts of data from only one or two progeny at a time is added, the change in EBV accuracy can be minimal and take a long time for cumulative data records and hence EBV accuracy to reach high levels. The graph (page 23) shows gradual changes in EBV accuracy over 3.5 years for two sires born between 2011 and 2015, each with a varying amount of data available from relatives.

In Figure 1, we can compare the rate of increase in EBV accuracy for the Gestation Length and Birth Weight traits. In this example, we can see that the EBV accuracies for Sire 1 and Sire 2 for the Gestation Length trait are lower than the EBV accuracies for the Birth Weight trait at all three time points for each sire. This is due to the low heritability of Gestation Length (0.21) compared to Birth Weight (0.37). Genetic and progeny data for the Birth Weight trait adds significantly more information to the Birth Weight EBV accuracy.

With increasing amounts of progeny data included in Figure 1, we can see that the EBV accuracies for the two traits increases slowly but gradually over time. This can be compared to changes in EBV accuracy shown in Figure 2 below for sires 3 and 4, who were both born in 2019 and entered into Cohort 1 of the AWA Progeny Test Program as rising two year-olds.

BREEDPLAN

BREEDPLAN

BREEDPLAN

OCTOBER 2021 RUN

DECEMBER 2022 RUN

FEBRUARY 2023 RUN 1

2023 RUN 2

Figure 2 Changes in Birth Weight (BW) and Gestation Length (GL) EBV accuracies for two Progeny Test Program Sires entered in Cohort 1 with only PTP Progeny registered and analysed in the October 2021 BREEDPLAN (when they were accepted into the Program) to the February Run 2 2023 BREEDPLAN.

GESTATION LENGTH (GL)

In Figure 2, we can see that Birth Weight and Gestation Length accuracies jumped significantly in just 16 months, with the registration and analysis of only PTP Progeny across six Contributor Herds.

This impressive increase in accuracy is made possible by having progeny analysed in large contemporary groups with progeny from multiple other sires and with strong genetic linkage across herds. Even for the Gestation Length EBV, which has low heritability relative to Birth Weight, because of the large contemporary group size, with multisire data, the change is EBV accuracy is considerable. The EBV accuracy change for Birth Weight is also very effective, with the current EBV accuracy for Sire 3 and 4 at 87% with 22 and 26 progeny recorded respectively.

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Impact of progeny recording on EBVs and EBV accuracy to improve your breeding program

As described in this Wagyu Quarterly Update (see Page 18), members who contribute data on progeny in their herds can improve the EBV estimate for their animals, as well as increase the EBV accuracy and hence the reliability of the EBVs for the animals they are using in their breeding programs.

Providing performance data to AWA will improve the estimate of the genetic merit of the breeding animals you are using and the estimate of the genetic merit of the progeny you choose to keep for future breeding generations. If you are collecting this data on your animals, obtaining additional value through sending your data to AWA to improve your EBVs is at no additional financial cost to you, the AWA pays all data entry fees and BREEDPLAN fees.

In addition to entering your own data, as shown in figure 2 (page 24), entering sires in the AWA Progeny Test Program rapidly improves EBVs for traits and EBV accuracies, enabling breeders to make more reliable breeding decisions within their own operation sooner.

80% of AWA Progeny Test Program Cohort 1 calves are now registered with important birth data submitted to

BREEDPLAN. It is expected that the accuracies for other traits will follow the same trend as data is submitted for weaning, growth, feedlot and eventually carcase and reproduction traits.

Not only will the AWA-PTP create high accuracy EBV’s for project sires and cows, but it is also designed to benefit all AWA members through maximising genetic linkage and genomic analysis power within BREEDPLAN. In time, this will further improve the breeding decisions and rate of genetic improvement in Wagyu across all participating herds and sire owners.

Your chance to gain maximum benefits for your sires and herd

AWA members are urged to become involved in the program and nominate their sires to further enhance their Wagyu genetics.

Any Australian or international based AWA member can nominate sires for the AWA-PTP, giving an opportunity for all AWA members to have their next generation of sires proven through the program for current and new traits. There is also the opportunity for cow herds to be bench marked, with a minimum of 150 second-calf females to be submitted.