Use this page to learn how BW, PW and LW can be used, benchmark your herd or individual cows and check out how the genetic merit of the national herd is trending over time.
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BW, PW, LW explained
Cow indices are available to help farmers make decisions about their cows.
Information that is collected on farm, such as herd testing, mating and calving data is incorporated into each index.
BW and PW are reported with an associated reliability: this gives an indication of how accurate you should expect the number to be.
$82/55 = BW of $82, with a reliability of 55%
Heifer replacements will typically have BW reliabilities of around 40%, this will increase as they enter the dairy herd and begin to accumulate records in their own right.
BW (Breeding Worth)
This index measures the expected ability of the cow or bull to breed replacements which are efficient converters of feed into profit.
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Reliability
BW and PW are reported with an associated reliability: this gives an indication of how accurate you should expect the number to be.
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PW (Production Worth)
This index measures the ability of the cow to convert feed into profit over her lifetime.
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- A high reliability PW is based most strongly on the cow’s herd testing history
- A low reliability PW is based most strongly on ancestry
- Typically a well-recorded heifer starts her life with a PW reliability of about 20%; by the time she has 5 recorded lactations, and some liveweight recording, the reliability will be about 85%
- A PW of 78/56 indicates that the cow is expected to generate an extra $78 net farm income per year (per 5 tonnes of feed on a dry matter basis) with a reliability of 56% compared to a cow with a PW of 0
- The main use for the PW is for purchasing and culling decisions
LW (Lactation Worth)
This index measures the expected ability of the cow to convert feed into profit in the current season.
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- Early in the season the LW has to be estimated from very little information. For this reason, the LW is liable to change very noticeably during the course of the season
- A LW of $98 indicates that the cow is expected to generate an extra $98 net farm income per year in the current season (per 5 tonnes of feed on a dry matter basis) compared to a cow with a LW of 0
- The LW has limited use for decision-making. The reason for this is that some of the factors that affect a cow’s current performance will not apply in future seasons (e.g. temporary lameness).
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Herd Ranking
Look up where your herd sits among all the herds in the national herd.
The following table shows, where herds rank in relation to all herds (includes all current numbered cows aged over 490 days signed up for herd testing)
Top Median Bottom 5% 10% 25% 25% 10% 5% BW ($) >111.3 >102.8 >87.4 70.7 <50.9 <26.2 <7.3 PW ($) >141.6 >129.6 >111.2 91.0 <68.4 <44.4 <27.3 The above figures are from the Animal Evaluation run on 12 February 2018. These figures do not include genomics.
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Sire Ranking
Look up how a sire ranks against other sires with daughters in the national herd.
The statistics in the following table include all dairy sires who meet the following criteria:
- AE enrolled
- BW reliability of at least 60%
- At least 20 NZ daughters
- At least 1 two-year old daughter who has been herd tested in the last 5 years.
Breeding Worth (BW) Top Median Bottom 5% 10% 25% 25% 10% 5% Ayr 32.9 16.5 -28.0 -73.9 -140 -221.0 -270.4 FxJ 197.3 179.9 142.2 104.6 60.9 22.8 5.7 HF 140.3 116.8 75.5 11.2 -74.8 -161.9 -206.6 Jer 192.8 165.9 122.0 75.7 16.0 -57.8 -113.5 To see ranking information for individual Breeding Values (BVs) click here.
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Cow Ranking
Look up where your cow sits among all the cows in the national herd.
The following table shows, where cows rank in relation to all cows in the country (includes all current numbered cows aged over 490 days in herds signed up for herd testing).
Top Median Bottom 5% 10% 25% 25% 10% 5% BW ($) >144.8 >129.7 >102.4 69.1 <32.4 <-2.6 <-26.3 PW ($) >246.6 >210.2 >151.7 89.4 <25.8 <-35.8 <-76.6 The above figures are from the Animal Evaluation run on 12 February 2018. These figures do not include genomics.
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Cow and Heifer Averages
Breeding Worth (BW) Averages Age All breeds Holstein-Friesian Jersey Ayrshire H-FxJ MA Cows 64.9 49.4 86.4 -57.4 75.3 2017 Born 104.1 88.6 121.5 -47.0 118.4 2016 Born 92.5 76.6 110.8 -50.2 106.2 2015 Born 80.5 66.4 102.5 -54.4 92.2 Production Worth (PW) Averages Age All breeds Holstein-Friesian Jersey Ayrshire H-FxJ MA Cows 87.8 60.6 91.4 -21.6 107.9 2017 Born 111.2 86.9 110.8 -24.5 132.8 2016 Born 102.2 78.6 98.1 -25.6 123.5 2015 Born 96.1 72.0 98.0 -30.5 117.6 Note: Averages for MA cows include all cows tagged in herds which have more than 80 cows, and are signed up for herd testing in the current season. Heifer averages (2015, 2016 and 2017 born) include all females current in dairy herds.
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Genetic Trends in the National Herd
On average, milk solids production has increased by about 50kg/cow over the past ten years. It is estimated that around 42% of those production gains are a direct result of farmers commitment to genetic improvement.
Alongside these production gains, the genetic merit of the national herd has also improved or held steady across a wide range of economically important traits.
The graphs below show how the genetic merit of cows in the national herd is trending for individual traits.
Breeding Worth: $8.73/year (10 yr), $9.70 (5yr)
The rate of genetic gain in Breeding Worth is increasing over time and currently sits at around 1.38% per year. The following graph shows the average BW of cows by year born. The 10 year average rate of gain is $8.73/year. The 5 year average rate of gain is $9.70/year.
Production Efficiency
Robustness
Traits other than Production
Note: Genetic Trend data is current as at June 2016. All cows born in each year are included in the averages, with the exception of animals who do not have any calvings or matings recorded by the age of three years old.
Click here to download the Updated Animal Evaluation Statistics