NZ animal evaluation

LIC first introduced this system to British farmers over 20 years ago and since then we’ve helped improve the long-term performance of many dairy herds across the United Kingdom.

NZAEL aims to improve the genetic merit of the national dairy herd by identifying the animals whose progeny will be the most efficient converters of feed to farmer profit. 

As a subsidiary of DairyNZ, their job is to develop and deliver the technologies that publish the independent evaluation of all New Zealand dairy animals using the Breeding Worth (BW) index. This is the critical information farmers use to help breed animals that increase both the genetic gain of their herds and their farm profit.

NZAEL’s guiding principles are:

  • Establish consistency across all genetic analyses where possible.
  • Identify animals whose progeny will be the most effective converters of feed into farmer profit.
  • Incorporate state-of-the-art animal evaluation systems.
  • Be totally transparent.

How NZAEL works

NZAEL captures, analyses and applies real animal data to the New Zealand dairy cattle database. Both male and female cattle are evaluated for their genetic merit.

Daughters of bulls are assessed and ranked within their contemporary group for a set of important genetic traits that drive profitability.

Information collected by the industry is used by NZAEL to estimate breeding values (BVs). Records utilised include: milk production, somatic cell count, liveweight, body condition, mating, calving and removals, and traits other than production (TOP). 

Farmers report management, or workability traits, while trained inspectors report dairy conformation and type traits. Approved milk recording companies contribute milk production records.

Breeding Worth (BW)

The Breeding Worth (BW) index ranks male and female animals for their expected ability to breed profitable, efficient replacements.

BW helps farmers achieve greater genetic gains faster, which means you can increase your farm profit more and more each year.

The index combines selected genetic traits with the economic contribution of those traits to farm profit. Trait breeding values (BVs) are multiplied by economic values (EVs) in the formula:


The resulting profit index is Breeding Worth (BW), measured in NZ dollars and reported relative to a genetic base benchmark, which is set at zero.

For example, if a bull has a BW of 200, his offspring will receive half of his genetic merit and are expected to earn the farmer $100 more than the genetic base cow per year.


The other number that is reported alongside BW is reliability. Reliability measures how much information has contributed to the BW evaluation for an animal. It is shown on a scale of 0 to 100%. For example, reliabilities closer to 100% represent more information on progeny and ancestors being available for that bull.

High-reliability bulls are unlikely to have large shifts in their BW when more daughters are added. In contrast, bulls with lower reliabilities are more likely to have larger shifts in their BW as more daughters are added.

Breeding values

A breeding value (BV) is an estimate of a dairy cow or bull’s  genetic merit for a trait. Using breeding values to select cows and bulls to parent the next generation is the most effective way to achieve genetic improvement. NZAEL use practical data collected on-farm to calcuate BVs.

There are 10 main breeding values that make up the Breeding Worth (BW) index:

Production efficiency traits

  • Milk protein
  • Milk fat
  • Milk volume
  • Liveweight

Robustness traits

  • Somatic cell score
  • Fertility
  • Gestation length
  • Functional survival
  • Body condition score
  • Udder overall.
Effective emphasis on individual traits within bw graph_Mar 23 2

These traits are also relevant to dairy herds across the United Kingdom.

Economic values

Economic values (EVs) are an estimate of the value of a trait to a NZ dairy farmer. Breeding with this system helps dairy farmers improve profitable traits.  

The economic values influence the effective emphasis of each trait in BW and use the costs and income sources on farm relating to the trait.

Economic values are adjusted annually to ensure BW remains relevant in an ever-changing market environment.

BW is measured across all breeds and breed mixes in New Zealand, giving a single across-breed BW figure. This means animals can be directly compared for their breeding value regardless of breed or breed mix.

The way the animals are measured across breed is unique to NZ. All other countries compare cows within breed.

Bulls can be compared both within and across breed groups in the bull rankings of active sire list (RAS list) by Dairy NZ.

Comprehensive genetic evaluation information including means, standard deviations and percentiles across the main dairy breeds at a herd, and cow or enrolled sires level is available in the Animal and Herd Averages section of the website.

LIC’s NZ cow indexes, production worth (PW) and lactation worth (LW), are also across-breed indexes. PW calculates the profit expected from a dairy cow in the current season. LW calculates the expected lifetime profit. NZ farmers use these indexes to directly compare the profitability of dairy cows of differing breeds in their own herd and farm system.

Download the Breeding Worth Explained brochure for more information on BW, PW and LW.

Genetic trends

The genetic merit of the population should continually improve in a successful breeding programme. This is called genetic gain, as each generation builds on the genetic merit of the previous one.

The rate of genetic gain in New Zealand is BW $10/ year, on average, as animal efficiency increases. Average per cow production has increased by 50 kg milk solids in the past 10 years, while liveweight remains relatively static. Researchers estimate 40% of this production gain is due to genetic improvement.

For more detail on genetic trends view the NZAEL website.

TOP traits

In addition to production and robustness traits, it’s desirable to see genetic gain for other important non-production traits such a temperament, udders and dairy conformation.

These traits are called Traits Other than Production (TOP) and fall into two categories – management traits and conformation traits.

Management traits are farmer-scored and include:

  • adaptability to milking
  • parlour temperament
  • milking speed
  • overall opinion
  • heifer calving difficulty
  • cow calving difficulty.

Conformation traits are scored by an inspector and include:

  • Stature
  • Capacity
  • Rump Angle
  • Rump Width
  • Legs
  • Udder Support
  • Fronty Udder
  • Rear Udder
  • Front Teat Placement
  • Rear Teat Placement
  • Teat Length
  • Udder Overall
  • Dairy Confirmation 

Download the TOP booklet for more details.

Introducing these beneficial traits into herds across the United Kingdom will contribute to longer lasting, healthy cows that will benefit the dairy farming gene pool and industry as a whole.

The Genetic Base

It is helpful to have a benchmark when ranking within a population. In animal evaluation, this reference point is called the genetic base – also known as the base cow.

A group of well-recorded cows from a selected year makes up the genetic base. Their profitability is set to the reference point of zero and all animals are reported in relation to this group. If an animal is more profitable than the genetic base, the BW value will be positive. If less profitable, the BW value will be negative.

The genetic base is updated every five years. A new group of cows for the genetic base is selected from a group five years on from the previous base. Although they are genetically superior to the previous base, the new BW is set to zero as the reference point.

The result is a national herd reset with an overall drop in BW seen each base change year, as the new genetic base becomes closer to that of the current population.

Visit the NZAEL website for more information

NZ animal evaluation contents

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