This round of improvements, collectively referred to as NZAEL 3.0, includes new data filters and model updates based on research findings and farmer feedback, as well as significant investment in the software and systems used in the evaluation.
As always, these changes have been rigorously tested by the Farmer Advisory Panel (FAP) and internationally peer-reviewed by the Scientific Advisory Committee (SAC) before final sign-off from the NZAEL board.
LIC and CRV work closely with NZAEL, and their partners, and are incorporating the latest enhancements from NZAEL 3.0 into their in-house genomic evaluations, MINDA and MyHERD reporting systems.
Expect to see further NZAEL improvements in the pipeline, the next of which is scheduled for April 2022.
What to expect when NZAEL 3.0 launches
The annual update in economic weightings in the Breeding Worth (BW) index has been moved from February to December, and this will coincide with the NZAEL3.0 launch. This means not all changes in BW values and sire rankings at launch time are due to the new NZAEL 3.0 model improvements.
Higher milk returns have meant that the economic values used to weight the fat and protein breeding values, have both increased by nearly $1/kg in the Breeding Worth index. There have also been increases in the economic value weightings for Fertility, Body Condition Score (BCS), and a stronger penalty for Somatic Cell Count (SCC). Overall, these annual updates to farm revenue and costs are driving about half of the reranking in sires that will occur when NZAEL 3.0 launches.
When the NZAEL 3.0 model improvements and the updates to the economic value weightings are implemented, the average bull will see an increase in its breeding worth value. The BW values for the most recent cohort of high-reliability sires, born 2010-2019, will gain $34 on average. This means breeding worth values for young stock, such as replacement heifers, are likely to increase after the NZAEL 3.0 launch.
The graph below shows the average change in BW for bulls born after 2010 with a BW reliability of at least 75%.
Older bulls are also expected to show an upward trend, although some older Jersey bulls’ values may devalue due to a higher economic weighting on milk solids and changes in the BCS breeding value (more info on the BCS change below).
Due to the nature and the number of changes/updates included in the release of NZAEL 3.0, farmers will no doubt have queries regarding their individual herds. Breeding companies will be able to assist their customers with understanding these new changes.
More information on NZAEL 3.0 improvements
Farmers drive more focus on udder conformation in NZAEL 3.0
Farmer feedback is an important part of ongoing NZAEL improvements as the industry works hard to move successive generations towards the ideal cow for NZ dairy farming in the future. Many farmers are seeking a stronger selection effort on traits related to cow robustness and longevity. Udder conformation is a particular priority because of increasing per cow production in some of the milking systems now in use throughout NZ.
NZAEL 3.0 will debut a teat length breeding value which has been in development since phenotypic measurement of rear teats began in 2017. This has not been incorporated into the breeding worth index so will not influence sire rankings. But the teat length trait will provide extra information for farmers who are concerned about teats becoming too short for their milking equipment.
The teat length trait joins the five existing udder traits reported as stand-alone breeding values that assess udder strength and teat placement. There is also an 'udder overall' trait which summarises the udder traits into a score for overall udder conformation. A recent stakeholder survey indicated that farmers would like the existing 'udder overall' trait incorporated into the Breeding Worth index. NZAEL and the wider NZ dairy genetics community are expecting to incorporate 'udder overall' into the breeding worth index during 2022, following the usual scrutiny of the peer-review process.
NZAEL 3.0 features improved breeding values for fertility and cow survival
More accurate breeding values lead to greater genetic gains for dairy farmers. Knowing this, DairyNZ scientists, together with experts from throughout the dairy industry, continue to research new ways of assessing traits. Following nearly a decade of DairyNZ-led research, NZAEL 3.0 contains key updates to the breeding values for fertility and cow survival.
The lag time to obtain reliable predictions from offspring is a major limitation to improving both traits. For fertility, good predictions were not available until a bull’s daughters were bred for their second season. Information on daughter survival only became available as daughters were culled. NZAEL 3.0 includes earlier indirect predictions of these traits to help identify promising young bulls before all this information is available.
NZAEL 3.0 also includes better algorithms to assess data quality. Not every commercial dairy herd records accurate calving and culling data. In the past, this has eroded the quality of the fertility and residual survival breeding values once a bull has graduated to commercial use. NZAEL 3.0 has improved methods to filter out records containing inaccurate or improbable information.
What’s new for fertility predictions?
NZAEL 3.0 makes greater use of calving records to construct the fertility breeding value.
Starting in the first calving, it uses calving season day (the number of days between the herd’s planned start of calving and a cow’s calving date) to assess fertility success. This adds to the existing, cruder, assessment of whether a cow was mated in the first 21 days of mating (PM21) and/or calved within the first 42 days of calving (CR42).
The new fertility breeding value rewards the cows that calve earliest. Meanwhile cows that calve later, are culled for poor fertility, or fail to calve in the subsequent season are penalised. The new Fertility breeding value will continue to use the existing CR42 scale for reporting. There are more improvements in the fertility breeding value making their way through the NZAEL research, development, and approval processes.
What’s new for cow survival predictions?
A new 'Functional Survival' breeding value replaces 'Residual Survival' in the Breeding Worth index.
Like its predecessor, Functional Survival incorporates direct cow culling for reasons other than poor fertility or low milk production (i.e., traits already incorporated in the Breeding Worth index). But the Functional Survival breeding value also makes use of several predictor traits collected during daughter TOP inspections of pedigree and sire-proving herds.
These indirect predictor traits include the conformation of the legs and udder, as well as milking speed and body condition score. Functional Survival reflects cow survival from one lactation to the next. This change allows for prediction of survival at different stages of life.
NZAEL 3.0 provides better breed neutrality for body condition score
The ideal NZ dairy cow produces well without losing too much body condition over the milking season. The BW ranking uses measurements of body condition score (BCS) derived from sire-proving daughter inspections, alongside lactation information, to up-rank bulls whose daughters produce well while maintaining good body condition scores. However, it is difficult to compare BCS breeding values between, say, a Jersey cow and a Holstein-Friesian cow, because there are fundamental differences in the way each breed exhibits their fat reserves throughout the milking season. Therefore, BCS breeding values must be adjusted within the NZAEL system to fairly compare breeds.
Methods for handling these breed differences need to be periodically reviewed to ensure they are achieving breed neutrality. NZAEL 3.0 contains an updated system for adjusting BCS. As NZAEL 2.0 unintentionally favoured the Jersey breed by around $10 of BW value, providing better breed neutrality in the BCS breeding value will result in a drop in BCS BVs for the Jersey breed and an increase in Holsteins and Ayrshires. However, when other NZAEL 3.0 changes are considered via the overall Breeding Worth index, the Jersey breed remains competitive amongst the team of top sires.
The improved accuracy in the BCS breeding value will provide more effective genetic selection across the national dairy herd, regardless of breed.
What’s new in the NZAEL 3.0 data handling system?
The data handling and processing systems in NZAEL have been built from the ground up to future proof NZAEL as an independent and transparent system for genetic evaluation. BOLT, a NZ-lead software system already used in international breeding programmes, has been selected for this task because it is well suited to the collaboration and testing that is integral to the ongoing improvements in the NZAEL evaluations. BOLT is also a powerful option for performing genomic predictions.
The NZ dairy industry will be incorporating genomic information into the independent NZAEL evaluations over the coming year for the next major update, known as NZAEL 3.5.
What is in the 2022 pipeline?
There are more improvements coming through the NZAEL peer-review pipeline.
In 2022, NZAEL is planning to deliver improved breeding values for the Calving Difficulty (a.k.a. Calving Ease), Gestation Length and Liveweight traits. In addition, work is already underway to include the Udders Overall trait in the Breeding Worth index and NZAEL continues to progress towards the NZAEL 3.5 model which will include genomic predictions.