Animal evaluation

 The calculation takes into account: 

• milk production 
  
• income from cull cows and bobby calf sales
  
• costs in generating and rearing replacements
  
• dairy cash expenses. 

EVs are recalculated every February and published on the DairyNZ website. 

Find out more about EVs on the DairyNZ website.

The more ancestry information, animal's own records (herd tests), and progeny information included, the more confidence you can have in the estimate of the evaluation. 

The higher the reliability the less likely it will change significantly with additional records. 

NZAEL are responsible for sire BW and determining the traits included. If an update is made to sire BW, the same update is applied to cow BW. 

A cow’s BW is based on ancestry, individual and offspring records. A bull’s BW is based solely on ancestry information, until it has daughters with records. BW incorporates eight breeding value (BV) traits – traits that have been recognised as having the greatest impact on farmer profitability. It is comparable across all herds, ages and breeds. 

A cow with a BW of 110 indicates the cow is expected to breed daughters that are $55 more profitable, per year, per unit of feed, than daughters of a cow with a BW of 0. 

Information that contributes to evaluating a cow’s worth

A cow’s BVs takes into account three types of records: 

1. Ancestry (all female relatives related through ancestry such as sisters and nieces) – used when she’s a calf.
   
2. Own performance (once she is milking). 
   
3. Performance of offspring (or direct descendants) – included once she has herd-tested daughters.

An untested cow is evaluated solely on its ancestry records. As the number of lactations and herd tests increases, her own performance starts contributing to her BW estimate, although ancestry still plays a dominant role. The true indicator of a cows' ability to generate profitable replacements is through the performance of her progeny (daughters or daughters of sons).

The diagram below shows the weightings for a cow’s BVs at different stages of her herd life. The increased weighting on progeny information reinforces the definition of BW. 

Ancestry/own lactation/progeny information weighting in cow BV

To calculate the BW of a cow, multiply its BVs by the EVs and add together. Cow BVs are shown on a MINDA Trait Evaluations report. 

Find out more about Breeding Worth on the DairyNZ website.

Like cow BW, PW (and PVs) is also based on ancestry, individual and offspring records. Cows are given PVs for five individual traits: 

• protein
  
• fat
  
• volume
  
• liveweight
• somatic cell.

These are then combined into a PW using EVs.

A cow with a PW of 98 indicates the cow is expected to generate $98 more profit in each of her lactations, than a cow with a PW of 0. 

The weighting placed on a cow’s own records is much greater than those for ancestry and offspring when calculating PVs (see the diagram below). This is because PVs/PW measure the lifetime producing ability of the cow herself, not what she is expected to pass on to offspring. It's important to note, herd test records collected on animals eight years or older don’t feed into the PW estimate. If a cow is still in the herd at this age she has already justified her presence in the herd. This herd test information does go into LW though.

Ancestry/own lactation/progeny information weighting in cow PV

Calculate PW using the MINDA Trait Evaluations report and multiply each PV by its respective EV. 

PW is comparable across all herds, ages and breeds. It’s designed to provide an accurate and objective calculation to aid farmers’ decisions related to culling and buying dairy cows.

More information about the 2018 PW update.

A cow’s LW combines her current-season producing ability for: 

• protein 
  
• fat
  
• milk volume
  
• liveweight. 

LW is based on a cow’s own herd test records as well as liveweight. 

A cow with an LW of 140 indicates the cow is expected to generate $140 more profit than a cow with an LW of 0. This is per unit of feed in the current season. 

EVs for LW are same as those used for PW. 

LW is comparable across all herds, ages and breeds. However, since LVs and LWs provide only a current season ranking of a cow’s profit and efficiency (rather than a lifetime ranking), their usefulness is limited for long- term decision-making. Where LW is of use is for assessing the performance of older cows in the herd. Once a cow reaches eight years of age, herd test information no longer contributes to the estimate of PW, but is still used in the estimate of LW. A drop in LW from one season to the next could indicate that a cow is potentially past her prime.