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NZAEL to deliver improved Breeding Values

By upgrading its genetic evaluation systems in a two-stage process, NZAEL is to deliver improved breeding values to New Zealand dairy farmers. The first stage takes place this year, the second in 2021.

• February 2020: NZAEL 2.0

  In February 2020, NZAEL will implement the most recent version of LIC’s genetic evaluation software (NZAEL 2.0). The upgrade to NZAEL 2.0 will incorporate improvements to the evaluation models, the software used for computing evaluations, and the post-processing adjustments that are applied to breeding values before they are published. 

  Model Improvements

  Inbreeding: The NZAEL 2.0 models account for inbreeding as a factor responsible for non-additive genetic effects. Breeding values represent additive genetic merit, and so by accounting for inbreeding, the models produce more accurate breeding values. Click here to read more about inbreeding.

  Differences between Holsteins and Friesians: The NZAEL 2.0 models treat Holsteins and Friesians as different breeds. This results in breeding values that more accurately reflect the differences between Holstein and Friesian animals. Also, accounting for effects of hybrid vigour in Holstein-cross Friesian cows improves the separation of additive and non-additive genetic effects, resulting in more accurate breeding values.

  Removing breed from genetic groups: All animals in an evaluation are grouped based on their demographics. With NZAEL 1.0, genetic groups were defined by age and breed. Under this design, the genetic groups should be capturing breed effects, and the breed-specific genetic trend. This created a complexity to the model that has grown over time. Because of this complexity, it is likely that the NZAEL 1.0 models were no longer solving correctly. This was leading to sub-optimal estimations of breed effects and genetic trends.

  The NZAEL 2.0 models separate the genetic trend from the breed effect by generating a fixed breed component for all ages. The genetic trend is then captured in the piece of the breeding value that is unique to the animal.  These models are a simplified system of equations which solve more readily.

  New Software for Computing Evaluations

  At the core of a genetic evaluation system are computer programs which fit the mixed models by forming and solving the model equations. In other words, the programs work with what we know, (performance and pedigree information, variances, and the mixed model equation) to predict the additive genetic merit of every animal.

  NZAEL 2.0 uses state-of-the-art computing software, which incorporates the last 13 years of technological advances. These improvements enable the hugely complex system of equations to be solved quickly and reliably. The new software is much faster with evaluations completing in less than 15 hours, roughly a quarter of the time taken by the NZAEL 1.0 software.

  Adjustments – removal and updating

  Over the years, a number of adjustments have been applied to the evaluations to increase their accuracy. These include the reproof adjustment, the parent average adjustment and the heterogeneous variance adjustment.

  1. The reproof adjustment was introduced to counteract a systematic drop in the BV of progeny tested sires as they attain daughters in the wider national herd (the reproof effect). The model improvements implemented on the 21^st of February have reduced the magnitude of the reproof effect, and so this adjustment has been removed.
  2. The parent average adjustment addresses a systematic drop in the BV of young sires gaining their first daughter proof (progeny test proof). It’s likely that the parent averages of animal evaluation (AE) enrolled sires are overestimated due to sub-optimal partitioning of additive and non-additive genetic effects and permanent environmental effects in their highly selected elite mothers. This adjustment is still required, and the factors applied to reduce the parent average breeding values for AE-enrolled sires have been updated.
  3. The heterogeneous variance adjustment was originally designed to adjust the performance of herds of cows to a common variance. The purpose of this adjustment was to give more accurate evaluations. A substantial amount of research established that this adjustment was not significantly improving the evaluation system, and so it has not been included in NZAEL 2.0.

• February 2021: NZAEL 3.0 (Genomics)

  A strong industry collaboration is being established between LIC, CRV, DairyNZ and other cattle breeding stakeholders. The objective of this collaboration is to deliver a national genomic evaluation system for New Zealand dairy farmers.

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There are currently eight traits that have been identified as having a measurable economic value to NZ farmers, and these breeding values are combined with the relevant economic values to produce Breeding Worth (BW).

Breeding Worth is the industry index which ranks cows and bulls on their ability to breed profitable and efficient replacement dairy heifers.

Breeding Values Explained

Breeding values are calculated using information which is collected by farmers, on-farm. For example:

• Herd Testing data
• Weighing data
• Body Condition Scores (when collected for each individual cow)
• ‘Traits other than production’ scores

Cows which are routinely measured will have more accurate breeding values.

When a heifer calf is born, her initial breeding values will be calculated as an average of her parents. This means that is it crucially important that the mother of a calf is identified correctly at birth.

The accuracy of a bull’s breeding values increase as more of his daughters are measured.

Production Efficiency

Robustness

The Animal Evaluation system is able to produce breeding values for a total to 27 different traits. In addition to the traits included in Breeding Worth, farmers are able to access Breeding Values for a full range of TOP traits (Conformation and Udder traits) as well as gestation length, calving difficulty and lactation persistency.

• Additional Traits

  Gestation Length

  Gestation length breeding values are estimated from the difference from a progenies planned calving date and her actual date of calving. Sires with negative gestation length breeding values will ensure that gestation lengths of progeny born are shorter than 282.5 for males and 281.2 days for females. Gestation length breeding values are changing little over time.

  Calving Difficulty

  Calving difficulty breeding values are estimated from calving assistance information collected in progeny test herds only or cows that have been TOP inspected as heifers. Sires with negative calving difficulty breeding values will produce progeny that cause less calving difficulties than average.

Farmer Opinion Traits

Farmers with progeny test herds assess heifers for ‘opinion’ traits. This data feeds into their breeding values, as well as those of their sire and dam.

Click the arrows on the slider below to learn what each score represents, and how you can use them to breed improved temperament in your herd.

Body and Dairy Conformation Traits

Cows can be assessed by certified TOP inspectors for a range of body conformation traits. This data feeds into their breeding values, as well as those of their sire and dam.

Click the arrows to learn what each score represents, and how you can use them to breed improved conformation in your herd.

Udder Conformation Traits

Cows can be assessed by certified TOP inspectors for a range of udder conformation traits. This data feeds into their breeding values, as well as those of their sire and dam.

Click the arrows to learn what each score represents, and how you can use them to breed improved udders in your herd.