Page 6 - Glenside 2020
P. 6

EBVs Explained

        An animal’s breeding value is its genetic merit, half of which will be passed on to its progeny.
        While we will never know the exact breeding value, for performance traits it is possible to
        make good estimates.  These estimates are called Estimated Breeding Values (EBVs).
        In the calculation of EBVs, the performance of individual animals within a contemporary
        group is directly compared to the average of other animals in that group.  A contemporary
        group consists of animals of the same sex and age class within a herd, run under the same
        management conditions and treated equally.  Indirect comparisons are made between
        animals reared in different contemporary groups, through the use of pedigree links
        between the groups.
        EBVs are expressed in the units of measurement for each particular trait.  They are shown
        as + ive or - ive differences between an individual animal’s genetics difference and the
        genetic base to which the animal is compared.  For example, a bull with an EBV of +50 kg
        for 600-Day Weight is estimated to have genetic merit 50 kg above the breed base of 0 kg.
        Since the breed base is set to an historical benchmark, the average EBVs of animals in each
        year drop has changed over time as a result of genetic progress within the breed.
        The absolute value of any EBV is not critical, but rather the differences in EBVs between
        animals.  Particular animals should be viewed as being “above or below breed average” for a
        particular trait.
        Whilst EBVs provide the best basis for the comparison of the genetic merit of animals
        reared in different environments and management conditions, they can only be used
        to compare animals analysed within the same analysis.  Consequently, Simmental
        BREEDPLAN EBVs cannot be validly compared with EBVs for any other breed.
        EBVs are published for a range of traits covering fertility, calving ease, milking ability,
        growth, and carcase merit.  When using EBVs to assist in selection decisions it is important
        to achieve a balance between the different groups of traits and to place emphasis on those
        traits that are important to the particular herd, markets and environment.  One of the
        advantages of having a comprehensive range of EBVs is that it is possible to avoid extremes
        in particular traits and select for animals with balanced overall performance.
        Calving Ease EBVs (%) are based on calving difficulty scores, birth weights and gestation
        length information.  More positive EBVs are favourable and indicate easier calving.

         - CE % Dir = Direct Calving Ease - The EBV for direct calving ease indicates the
        influence of the sire on calving ease in purebred females calving at two years of age.
         - CE % Daughters = Daughters’ Calving Ease - The EBV for daughters’ calving ease
        indicates how easily that sire’s daughters will calve at two years of age.
        Gestation Length EBV (days) is an estimate of the time from conception to the birth of
        the calf and is based on Artificial Insemination and hand mating records.  Lower (negative)
        Gestation Length EBVs indicate shorter gestation length and therefore easier calving and
        increased growth after birth.


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