Breeding Values

Breeding Values (BV) are an estimate of a cow or bull's genetic merit for a trait.

There are currently eight traits that have been identified as having a measurable economic value to NZ farmers, and these breeding values are combined with the relevant economic values to produce Breeding Worth (BW).

Breeding Worth is the industry index which ranks cows and bulls on their ability to breed profitable and efficient replacement dairy heifers.

Breeding Values Explained

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

Herd Testing data
Weighing data
Body Condition Scores (when collected for each individual cow)
‘Traits other than production’ scores

Cows which are routinely measured will have more accurate breeding values.

When a heifer calf is born, her initial breeding values will be calculated as an average of her parents. This means that is it crucially important that the mother of a calf is identified correctly at birth.

The accuracy of a bull’s breeding values increase as more of his daughters are measured.

Production Efficiency

Robustness

Somatic cell score

Somatic cell score has a heritable of 15%. You should aim to lower somatic cell score breeding value over time. (Negative is best). Somatic cell score breeding values have been slowly decreasing since 2004, when the trait was introduced into BW.
- read more
  
  On average, Ayrshires have the lowest somatic cell score breeding value.
  
  Somatic cell score (SCS) breeding values are estimated from information derived from herd testing. Somatic cell count are log transformed and expressed as SCS. Assuming an average SCC of 150,000, -1 SCS is roughly equivalent to -75,000 SCC.
  
  This is information is then run through a test day model, where each animal is compared relative to her contemporary group (all animals with the same age (e.g. lactation 1, 2, 3, 4-6 or >6), year, season of calving and test day) with other main adjustments including permanent environmental effect (e.g. effect of rearing to two years of age), days in milk at test and hybrid vigour.
  
  The method to estimate breeding values also includes the genetic relationship between individuals in his or her pedigree who may have left equal, better or worse than average progeny for somatic cell score.
  
  More detail? Description of Genetic Evaluation System View PDF (127 kb)

Fertility

Fertility is a low heritability (9%) trait. You should aim to increase fertility breeding value over time. Genetic losses were observed from 1990 to 2000, but genetic gains have been made since 2002 when the fertility breeding value was first included in BW.
- read more
  On average, Jerseys have the highest fertility breeding value.
  
  Fertility breeding values (% calving within 42 days of the start of calving) are calculated from information derived from herd recording software such as MINDA and MISTRO, herd testing and Traits Other Than Production (TOP) assessments. Eight individual predictor traits are currently used to estimate the fertility breeding value:
  - Presented for mating within 21 days of the planned start of mating (PM21) in lactation 1, 2 and 3
  - Calving rate in the first 42 days after the planned start of calving (CR42) in lactation 2, 3 and 4
  - Volume in a cows' first lactation
  - Body condition score (BCS) in a cows' first lactation at 60 days in milk.
  All these traits are included as they are correlated (negatively or positively) with overall fertility. For instance, cows with genetically higher BCS have improved fertility, cows with genetically higher milk volumes have poorer fertility, and cows that are presented for mating within 21 days of the planned start of mating have improved fertility. Information from all these predictor traits are then run through a multi trait model, where each animal is compared relative to her contemporary group (all animals with the same age (e.g. lactation 1, 2, 3, 4-6 or >6), year and season of calving) with other main adjustments including permanent environmental effect (e.g. effect of rearing to 2 years of age), age and hybrid vigour. Again, the method to estimate breeding values also includes the genetic relationship between individuals in his or her pedigree who may have left better or worse than average progeny for fertility performance.
  
  More detail? Description of Genetic Evaluation System View PDF (55 kb)

Residual survival/Total Longevity

Residual survival is a low heritability (6%) trait which is derived from the Total Longevity breeding value. You should aim to increase Residual Survival over time.
- read more
  As the name would suggest, this breeding value represents 'residual' or 'uncounted' genetic merit for survival.
  
  All of the traits that are included in Breeding Worth have an impact on cow longevity. Fertility is a good example, as a big part of the value attributed to cow fertility is the increased profitability of a cow who survives from one season to the next. If total longevity was incorporated directly into Breeding Worth, those days of survival would be double counted.
  
  The solution to this is the Residual Survival BV, where the days of additional herd life which can be attributed to the existing BW traits have been removed.
  
  The equation that is used to achieve this takes into account the known relationships between cow survival, and each of the other BW traits. These relationships change over time, and so this equation will occasionally require an update to ensure it is accurate. The most recent update was in February 2016.
  
  Current equation:
  
  Total Longevity – [(4.848 X Fat) + (7.612 X Protein) - (0.0429 X Milk) - (1.5 X Liveweight) + (18.078 X Fertility) - (70.666 X SCC) + (364.931 X Body Condition Score)]
  
  Note: In Feb 2016 Body Condition Score (BCS) was incorporated into Breeding Worth. In response to this, the impact that BCS has on cow survival will be removed from the Residual Survival BV.
  
  Total Longevity
  
  The breeding value for longevity is calculated from information derived from herd testing, herd recording software such as MINDA and MISTRO, and Traits Other than Production (TOP) assessments.
  
  Four direct and nine predictor traits are currently used to estimate the longevity breeding value:
  
  Direct:
  - Survival from 1st to 2nd, 1st to 3rd, 1st to 4th, 1st to 5th lactation.
  Predictor:
  - Protein yield in lactation 1
  - Somatic cell score in lactation 1
  - Body condition score in lactation 1
  - Calving rate in the first 42 days after the planned start of calving (CR42) in lactation 2
  - Owner opinion in lactation 1
  - Milking speed in lactation 1
  - Leg conformation in lactation 1
  - Dairy conformation in lactation 1
  - Udder overall in lactation 1
  These traits are included as they are correlated (negatively or positively) with longevity. For instance, cows with genetically higher owner opinion, dairy and udder conformation have improved residual longevity. Cows with genetically higher somatic cell score have reduced longevity. Information from all these predictor traits are then run through a multi trait model, where each animal is compared relative to her contemporary group (all animals with the same age (e.g. lactation 1, 2, 3, 4-6 or >6), year and season of calving) with other main adjustments including permanent environmental effect (e.g. effect of rearing to 2 years of age), and hybrid vigour.
  
  The method to estimate breeding values also includes the genetic relationship between individuals in his or her pedigree who may have left better or worse than average progeny in terms of herd life.
  
  More detail? Description of Genetic Evaluation System View PDF (228 kb)

Body condition score

Body Condition Score is a moderately heritable (~25%) trait; you should aim to increase body condition score over time.
- read more
  Historically genetic gain in this trait has been minimal, but this is predicted to increase following the inclusion of the BCS in Breeding Worth (Feb, 2016).
  
  The body condition score breeding value is calculated using records collected on two year old heifers. These records are collected in early lactation, and the majority of them come from CRV and LIC progeny test herds.
  
  Raw scores are converted into a day 60 lactation equivalent, and then enter the AE model.
  
  As a result of a recent review (see below) a ‘breed neutral’ adjustment has been applied to this breeding value. This means that the breed average for this trait is 0 across all breeds.
  - BCS Breeding Value: 2014 Review
    NZAEL have completed a thorough review of the methods that are used to estimate a cows breeding value for body condition score. The review had three key focus points:
    
    To investigate whether BCS data collected on two year old heifers provided enough information to predict an animal’s lifetime genetic merit i.e. were genetically thin heifers also genetically thin older cows.
    
    To look at the correlation of early and late lactation BCS data, and determine whether data collected earlier in the season can be used to accurately predict late lactation body condition.
    
    To look into the breed differences which were apparent in the BCS breeding value, and determine if they were correctly representing the genetic differences in BCS between breeds.
    
    This review showed that the existing approach used to predict genetic merit for BCS was generally sound, and there was a strong genetic relationship between young and old cow BCS and early and late lactation BCS, particularly within breeds. However, it was found that when looking at breed averages, the differences in the BV were not consistent with actual observations in late lactation. As a result of these findings, and because the economic value for this trait is largely based on late lactation BCS, NZAEL began investigating ways in which this breed effect could be removed from the breeding value.
    
    Following industry consultation and a Technical review, the Standing Advisory Committee and the NZAEL board approved a method of removing these breed differences, which involves applying a ‘breed neutral’ adjustment. This process will strengthen the BCS breeding value, making it a more accurate prediction of an animal’s genetic merit for this trait.

The Animal Evaluation system is able to produce breeding values for a total to 27 different traits. In addition to the traits included in Breeding Worth, farmers are able to access Breeding Values for a full range of TOP traits (Conformation and Udder traits) as well as gestation length, calving difficulty and lactation persistency.

Additional Traits

Gestation Length

Gestation length breeding values are estimated from the difference from a progenies planned calving date and her actual date of calving. Sires with negative gestation length breeding values will ensure that gestation lengths of progeny born are shorter than 282.5 for males and 281.2 days for females. Gestation length breeding values are changing little over time.

Calving Difficulty

Calving difficulty breeding values are estimated from calving assistance information collected in progeny test herds and via data recorded in herd management software. Sires with negative calving difficulty breeding values will produce progeny that cause less calving difficulties than average.

Persistency

Persistency breeding values are estimated from test day milk yields and is the relative decline in milk yield from the first part to the second part of the lactation. Sires with positive persistency breeding values will produce progeny that have less of a decline in milk production in the second part of the lactation than average. Cows with persistent lactation curves (high persistency breeding value) can have high, average or low total lactation yields. The persistency measure is designed to be independent of total milk yield - so farmer should not use bulls with high persistency breeding values in an attempt to select for higher milk yields.

Farmer Opinion Traits

Farmers with progeny test herds assess heifers for ‘opinion’ traits. This data feeds into their breeding values, as well as those of their sire and dam.

Click the arrows on the slider below to learn what each score represents, and how you can use them to breed improved temperament 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

Cows can be assessed by certified TOP inspectors for a range of body conformation traits. This data feeds into their breeding values, as well as those of their sire and dam.

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

Cows can be assessed by certified TOP inspectors for a range of udder conformation traits. This data feeds into their breeding values, as well as those of their sire and dam.

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

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.
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.