Breeding Values

Protein

• Protein is a moderately heritable (31%) trait. You should aim to increase protein breeding value over time. Genetic gain has been around +1.1 kg/year, irrespective of breed.

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    On average, Friesians have the highest protein breeding value.

    Protein breeding values are estimated from information derived from herd testing. The production information which is collected for a cow during her first 6 lactations is run through a test day model. The test day model compares each animal to the other animals in her contemporary group (all animals with the same age group (2, 3, 4, 5 and mature), season of calving, test day and test year). Other main adjustments including removing the impact of permanent environmental effect (e.g. effect of rearing to two years of age), days in milk at test, hybrid vigour and induced calving.

    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 milkfat, protein or volume performance.

    More detail? Description of Genetic Evaluation System View PDF (43 kb)

Milk volume

• Milk is a moderately heritable (36%) trait. Genetic gain has been pretty consistent at around +19 litres/year with greatest rates of genetic gain in Friesians.

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    On average, Friesians have the highest milk breeding value.

    Milk breeding values are estimated from information derived from herd testing. The production information which is collected for a cow during her first 6 lactations is run through a test day model. The test day model compares each animal to the other animals in her contemporary group (all animals with the same age group (2, 3, 4, 5 and mature), season of calving, test day and test year). Other main adjustments including removing the impact of permanent environmental effect (e.g. effect of rearing to two years of age), days in milk at test, hybrid vigour and induced calving.

    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 milkfat, protein or volume performance.

    More detail? Description of Genetic Evaluation System View PDF (43 kb)

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.
  

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    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)

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.

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    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)

Changes to the way some mating data is treated within the fertility model have increased accuracy of sire BVs.