BLAIR SELECTION INDEX
    Blair Selection Index 
    Background to Blair Selection Index
    (Formulated by Professor Hugh Blair in Collaboration with the TRIGG group.)
    IN 2017 all breeders have been asked by Beef and Lamb to change to NZMW index which is very similar to our Blair index so we have done this

    The Blair selection index has been customised to reflect the performance of livestock on the farms of TRIGG ram-buyers. Customisation takes account of two aspects. Firstly the traits that are included in the Blair index, and secondly the economic weightings that are given to the traits. A list of these traits and the economic weights are given below.

    When deriving the TRIGG economic values, a farm model was built to describe animal performance under the conditions experienced on the farms of TRIGG ram-buyers. The model accounted for important income sources and for costs such as:

    • The feed required to support a ewe throughout her lifetime
    • The costs of rearing a replacement ewe
    • The extra feed costs associated with carrying multiple lambs during pregnancy, feeding them during lactation and feeding them to slaughter
    • The non-feed costs of rearing a lamb to slaughter
    • The non-feed costs of maintaining a ewe
    All of the following economic values are based on ewe lifetime performance; these are annualised so that economic values are per year.

    Number of lambs born (+$41.86 per extra lamb)

    An additional lamb born gives the opportunity to sell an extra lamb at some $80. However, not all of these lambs will survive, and the costs associated with rearing the additional lamb must be allowed for. Accordingly the value of the extra lamb is somewhat less than the market value of a lamb.

    Lamb survival (+$1.10 per 1% increase)

    To give an example of what this figure means, consider a farm with 120% of lambs born and a survival rate of 86%. This will give 103.2 lambs per 100 ewes available for sale (ignoring replacements). If the survival rate is lifted to 87%, 104.4 lambs per 100 ewes will be available. This is an increase of 1.2 lambs per 100 ewes or 0.012 lambs per ewe. If a lamb is worth $80, this gives an increased return of $0.96. The figure of $1.10 allows for the increased income and extra costs over a ewe’s lifetime.

    Hogget Pregnancy (+$5.20 per extra hogget pregnancy or $0.16 per 1% increase on hogget pregnancy)

    An additional lamb born to a ewe hogget gives the opportunity to sell one extra lamb per ewe lifetime at about $50. This one-off event must be distributed over the number of years the ewe is in the flock (currently set at 3.5 years), and the costs associated with rearing the additional lamb must be allowed for. Accordingly the value of an extra lamb is somewhat less than the market value of a lamb.

    Lamb growth genes (+$1.65 per kg increase in weaning weight)

    The weight that a lamb achieves at weaning is the combined effort of the lambs own growth genes (of which ½ are inherited from its sire and ½ from its dam) and the milking and protection provided by the dam. The extra income per kg of weaning weight generated by the growth genes has to allow for extra feed costs and the dressing out percentage of the lamb.

    Maternal genes for lamb growth (+$1.20 per kg increase in weaning weight)

    The main maternal contribution to extra weaning weight is through the dams milking ability. Any increase in milking ability must allow for the extra feed of generating the additional milk.

    Carcass weight (+$2.57 per kg increase in carcass weight)

    The additional economic benefit derived from an increase in carcass weight is calculated separately from the increase in weaning weight.

    Wool weight (+$3.00 per extra kg of wool)

    An extra kg of wool is near to the market value of wool because of the small feed cost of generating the extra wool. 

    Ewe feed efficiency (-$0.66 per kg of mature ewe liveweight)

    The ewe incurs some 70% of all feed costs in a farming system. As a consequence, it is important to explicitly allow for ewe feed costs. In placing downward selection pressure on ewe liveweight, it is important to recognise that this will affect the rate at which gains can be made in carcass weight. By taking later liveweights such as at 12 to 14 months a better separation of improving carcass weights and decreasing ewe liveweight can be made. New Paragraph

    List of Services

      Share by: