Breeding Values

Breeding Values (BV) reflect our knowledge of a cow or bull's genetic merit for a trait.

In April 2022, NZAEL launched the next round of enhancements to its genetic evaluation system for dairy bulls. Read more about these changes here.

Breeding Values Explained

A breeding value is an estimate of an animal's genetic merit for a particular trait. Breeding values define the superiority or inferiority of the offspring of an animal. An estimate of the breeding value for a particular trait is obtained from pedigree and performance information. Using breeding values to select cows and bulls to be the parents of the next generation is the most effective way to achieve genetic improvement.

The genetic relationships between an animal and all known ancestors and descendants are used when estimating breeding values to identify animals who are likely to produce progeny that is better or worse than average for each trait.

Importantly, breeding values for NZ dairy cattle can be compared across different breeds, herds, and ages.

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

Herd testing data
Scale liveweight data
Body condition scores (when collected for each individual cow)
Traits other than production (TOP) scores

Cows that are measured on more occasions will have more reliable breeding values.

When a calf is born, the first estimate of its breeding values will be calculated as the average of its parents. This means it is critically important that the mother of a calf is identified correctly at birth, as dam information is linked to the father of the calf through mating records.

The reliability of a bull’s breeding value for a particular trait increases as more of his daughters are measured in the same herd in comparison to daughters of other bulls.

The NZAEL Animal Evaluation system publishes breeding values for dairy bulls on a wide variety of traits. Nine of these traits have been identified as having a measurable economic value to NZ farmers, and those breeding values are combined with the relevant economic values to produce the index Breeding Worth (BW).

In addition to traits included in BW, farmers can access Breeding Values for a range of TOP traits (Conformation and Udder traits) as well as gestation length and calving difficulty in order to select bulls best suited to their herd.

Trait definitions

The nine traits in BW are categorised as either Production efficiency traits or Robustness traits.

Production efficiency

Protein yield, fat yield, milk volume

Breeding values for protein yield, fat yield, and milk volume are expressed as a whole season value.
Higher protein yield, fat yield or milk volume breeding values indicate a bull will have daughters that are expected to produce more protein, fat or volume than a bull used in the same herd that has lower breeding values for these traits.
- read more
  
  Breeding values for protein yield, fat yield, and milk volume are estimated using information that comes from herd testing during a cow’s first 6 lactations.
  
  The performance of each cow is compared with the cows in her herd that were tested on the same day, are of the same age and calved in the same season. This grouping of herd, test-day, age and season define each animal’s 'contemporary group'.
  
  The general assumption is that cows that perform better than other cows in their contemporary group (known as 'contemporaries') are of superior genetic merit and those that perform worse than their contemporaries have inferior genetic merit.
  
  That said, there are a range of factors that influence an animal’s performance and some of these factors are not passed on to subsequent generations. The effect of these non-heritable factors should be disregarded from breeding values. In the case of protein, fat and milk volume, these factors include stage of lactation, hybrid vigour, inbreeding, inductions and what is termed the ‘permanent environmental effect’ for example, the effect of rearing to two years of age.

Liveweight

Breeding values for liveweight are expressed as 5-year-old mature liveweight in kilograms.
A higher liveweight breeding value indicates that a bull will have daughters that are expected to be heavier than a bull that has a lower breeding value for liveweight.
- read more
  
  Breeding values for liveweight are estimated using information that comes from scale weight records of cows measured during one or more of their first 6 lactations.
  
  The weight of each cow is compared with the cows in her herd that were weighed on the same day, are of the same age and calved in the same season. This grouping of herd, weigh-day, age, and season define each animal’s 'contemporary group'.
  
  The general assumption is that differences among cows within a contemporary group have a genetic basis.
  
  That said, there are a range of factors that influence an animal’s liveweight and some of these factors are not passed on to subsequent generations. The effect of these non-heritable factors should be disregarded from breeding values. In the case of liveweight, these factors include stage of lactation, hybrid vigour, inbreeding, and what is termed the ‘permanent environmental effect’ for example, the effect of rearing to two years of age.

Robustness

Somatic cell score

Breeding values for somatic cell are expressed as an average somatic cell score (SCS) that is calculated by what is called a ‘log transformation’ of the somatic cell counts.
A lower somatic cell breeding value indicates that a bull will have daughters that are expected to have lower somatic cell counts than a bull that has a higher breeding value for somatic cell. In this case a negative breeding value is a good thing.
- read more
  
  Breeding values for somatic cell are estimated using somatic cell count information that comes from herd testing during a cow’s first 3 lactations.
  
  The somatic cell information of each cow is compared with the cows in her herd that were tested on the same day, are of the same age and calved in the same season. This grouping of herd, test-day, age and season define each animal’s 'contemporary group'.
  
  The general assumption is that cows that perform better (lower somatic cell) than other cows in their contemporary group (known as 'contemporaries') are of superior genetic merit and those that perform worse (higher somatic cell) than their contemporaries have inferior genetic merit.
  
  That said, there are a range of factors that influence an animal’s performance and some of these factors are not passed on to subsequent generations. The effect of these non-heritable factors should be disregarded from breeding values. In the case of somatic cell, these factors include stage of lactation, hybrid vigour, inbreeding, inductions and what is termed the ‘permanent environmental effect’ for example, the effect of rearing to two years of age.

Fertility

Breeding values for fertility are expressed as the percentage of cows calving within 42 days (6 weeks) of the start of calving.
A higher fertility breeding value indicates that a bull is expected to have more early calving daughters than a bull that has a lower breeding value for fertility.
- read more
  
  Breeding values for fertility are estimated using information that comes from calving and mating dates.
  
  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 in first, second, third and fourth calving.
  
  It also uses information collected before calving that reflects whether a cow was mated in the first 21 days of mating (PM21) during lactation 1, 2 and 3.
  
  The 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 calving or mating performance of each cow is compared with the cows in her herd that are of the same age and calved in the same year and season. This grouping of herd, age, year and season define each animal’s 'contemporary group'.
  
  The general assumption is that cows that perform better than other cows in their contemporary group (known as 'contemporaries) are of superior genetic merit and those that perform worse than their contemporaries have inferior genetic merit.
  
  That said, there are a range of factors that influence an animal’s performance and some of these factors are not passed on to subsequent generations. The effect of these non-heritable factors should be disregarded from breeding values. In the case of fertility, these factors include age at calving, hybrid vigour and inbreeding.

Functional survival

Breeding values for functional survival are expressed as the likely percentage of cows surviving to the next lactation independent of culling for low production or poor fertility.
A higher functional survival breeding value indicates that ignoring culling for low production or for low fertility, a bull is expected to have more daughters surviving to the next lactation than a bull with a lower breeding value for functional survival.
- read more
  
  Breeding values for functional survival are estimated using information from only those herds that provide high-quality data, reflecting direct cow culling for functional reasons other than poor fertility or low milk production.
  
  The survival performance of each cow is compared with the cows in her herd that are of the same age and calved in the same year and season. This grouping of herd, age, year and season define each animal’s 'contemporary group'.
  
  The general assumption is that cows that perform better than other cows in their contemporary group (known as 'contemporaries') are of superior genetic merit and those that perform worse than their contemporaries have inferior genetic merit.
  
  That said, there are a range of factors that influence an animal’s survival performance and some of these factors are not passed on to subsequent generations. The effect of these non-heritable factors should be disregarded from breeding values. In the case of functional survival, these factors include age at calving, hybrid vigour and inbreeding.
  
  Information on daughter survival only becomes available as a bull’s daughters are culled from herds that record the fates of cows. For this reason, to help identify promising young bulls prior to that time, the functional survival breeding value makes use of several predictor traits that are collected during 'Traits Other than Production' (TOP) inspections, these include the breeding values for conformation of the legs, and udder as well as milking speed and body condition score.
  
  As a bull’s daughters get older the reliance on the direct cow culling increases and the reliance on the predictor traits decreases.

Body condition score

Breeding values for body condition score (BCS) are expressed in BCS units and reflect the genetic merit for reserves of adipose tissue or fat.
A higher BCS breeding value indicates that a bull will have daughters that are expected to have higher BCS than a bull that has a lower breeding value for BCS.
- read more
  
  Breeding values for BCS are estimated using information from 2 year old heifers generally collected in early lactation with the majority coming from CRV and LIC progeny test herds.
  
  It is difficult to compare BCS breeding values between different breeds because there are fundamental differences in the way each breed exhibits their fat reserves throughout the milking season. Therefore, BCS breeding values have a 'breed-neutral' adjustment applied to fairly compare breeds. This means that the 2005 birth year average BCS breeding values for one breed are no different to the 2005 birth year average BCS breeding values of another breed.
  
  The BCS of each cow is compared with the cows in her herd that were scored on the same day, are of the same age and calved in the same year and season. This grouping of herd, score-day, age, year and season define each animal’s 'contemporary group'.
  
  The general assumption is that differences among cows within a contemporary group have a genetic basis.
  
  That said, there are a range of factors that influence an animal’s BCS and some of these factors are not passed on to subsequent generations. The effect of these non-heritable factors should be disregarded from breeding values. In the case of BCS, these factors include stage of lactation, hybrid vigour, inbreeding, and what is termed the ‘permanent environmental effect’ for example, the effect of rearing to two years of age.

Udder overall

Breeding values for udder overall are expressed as an overall score of udder conformation.
A higher udder overall breeding value indicates that a bull is expected to have daughters with more desirable udder conformation than a bull with a lower breeding value for udder overall.
- read more
  - Udder scores from first lactation (two-year-old) cows that are assessed by certified ‘traits other than production’ (TOP) inspectors are used to estimate breeding values for udder overall (as well as six other udder traits, described further down). Each scored heifer’s data feeds into their own breeding value, as well as those of their sire, dam and other relatives.
  - The udder overall score of each cow is compared with the cows in her herd that were scored on the same day, are of the same age and calved in the same year and season. This grouping of herd, score-day, age, year and season define each animal’s 'contemporary group'. The general assumption is that differences among cows within a contemporary group have a genetic basis. That said, there are a range of factors that influence an animal’s udder overall score and some of these factors are not passed on to subsequent generations. The effect of these non-heritable factors should be disregarded from breeding values. In the case of udder overall, these factors include age of the cow at calving, stage of lactation, hybrid vigour, and inbreeding.

Farmer opinion

Farmers that participate in progeny testing and 'Traits Other than Production' (TOP) assess first lactation (two-year-old) heifers for ‘opinion’ traits. Each scored heifer’s data is used to estimate their own breeding values, as well as those of their sire, dam and other relatives.

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

Farmers' score two-year-old heifers for four traits:

✓ adaptability to milking
✓ shed temperament
✓ milking speed
✓ overall opinion

In all cases, more positive values are better.
Adaptability to milking

• How quickly the animal adapts
to the milking routine.

• How long it takes for milk to be
let down spontaneously.
Shed temperament

• The temperament of the
animal in the shed after it
has settled into the
milking routine.
Milking speed

• The length of time it takes for
an animal to milk out.
Overall opinion

• A farmer's overall feeling
about the animal.

Body and Dairy Conformation Traits

Body conformation scores from first lactation (two-year-old) heifers that are assessed by certified TOP inspectors are used to estimate breeding values for the following six traits. Each scored heifer’s data feeds into their own breeding values, as well as those of their sire, dam and other relatives.

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

Stature

• Height measured at the
animal's shoulder.

• As breeding values are taken
across all breeds, Jerseys
tend to be negative on the
breeding values bar graph,
while Ayrshires are generally
intermediate and Friesians
positive.
Capacity

• Strength and depth of chest
and body as viewed from the
side.
Rump angle

• The angle between the middle
of the hip and top of the pin
bone.

• Negative breeding value
means the cow has high pins,
positive means the cow has
low pins.

• A flat to slightly sloping rump is
desired and scored at 5-6.
Rump width

• The distance between the
posterior point of the pin bones
in relation to the size of the
cow.

• Good indicator of the width of
a cow throughout her body.
Legs

• The angulation of the rear legs.

• This is measured from an
imaginary line between thurls
and mid-hoof while the cow is
walking.

• A low score indicates the cow
has a relatively straight leg set
while a high score indicates a
curved leg set.
Dairy conformation

• Overall conformation score
which combines all body
conformation traits.

Udder Conformation Traits

Udder scores from first lactation (two-year-old) cows that are assessed by certified TOP inspectors are used to estimate breeding values for the following seven udder traits. Each scored heifer’s data feeds into their own breeding values, as well as those of their sire, dam and other relatives.

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

Front teat

• Placement of front teats (where
attached to the udder) in
relation to the centre of the
quarters.

• Low score indicates wide front
teat placement while a high
score indicates close front teat
placement.
Rear teat

• Placement of rear teats (where
attached to the udder) in
relation to the centre of the
quarters.

• Low score indicates wide rear
teat placement while a high
score indicates close rear teat
placement.
Teat length

• Length of the rear teats from
the udder to the tip of the
teat.

• A score between 4 and 5
is optimum.
Udder support

• The strength of the suspensory
ligament as viewed from the
back.

• Udder depth relative to the
hocks of the animal.
Front udder

• The strength of attachment of
the front of the udder to the
body wall.
Rear udder

• The height and width of the
rear udder attachment as
distinct from udder support.
Udder overall

• Overall udder score which
combines all of the udder
conformation traits.

Additional traits

Gestation length

Gestation length breeding values are estimated from the difference between a cows planned calving date given her mating date, and her actual date of calving. Bulls with negative gestation length breeding values are expected to have calves that are born earlier than the average gestation length.

Calving difficulty

Calving difficulty breeding values are estimated from calving assistance information collected in progeny test herds or from cows that have been TOP inspected as heifers.

Bulls being used on yearling heifers should have a minus figure on calving difficulty with a greater minus indicating an easier calving sire.

NZAEL publishes heifer calving difficulty and cow calving difficulty breeding values for dairy bulls.

Read more
Heifer calving difficulty:
- The heifer calving difficulty breeding value for a sire is calculated from the difficulty its calves have, being born from a two-year-old dam.
- Sires with more negative heifer calving difficulty breeding values are expected to produce calves that exhibit less calving difficulties in first calving heifers than those with more positive breeding values for heifer calving difficulty.
Cow calving difficulty:
- The cow calving difficulty breeding value for a sire is calculated from the difficulty its calves have, being born from a three-year-old or older dam.
- Sires with more negative cow calving difficulty breeding values are expected to produce calves that exhibit less calving difficulties in cows aged 3 and over than those with more positive breeding values for cow calving difficulty.

Breeding Values

Breeding Values

Breeding Values

Breeding Values Explained

Trait definitions

Production efficiency

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Robustness

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Farmer opinion

Body and Dairy Conformation Traits

Udder Conformation Traits

Additional traits

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Breeding Worth

Economic Values

Reliability