Increasing ewe longevity and reproductive output can improve whole-flock efficiency and reduce environmental impact (Jones et al. 2013). By increasing ewe longevity (the length of productive life), fewer replacements are required, reducing the number of unproductive animals and increasing the number of ewe lambs to sell (Dickerson & Glimp 1975). Longevity research often looks for genetic indicators of this trait; however, heritability is low, or occasionally moderate (Mekkawy et al. 2009). An alternative approach may be to alter how animals are retained for breeding the following year, allowing animals to reach their potential and not reducing longevity by selling animals that are still productive. To achieve this, it is essential to be able to identify ewes that will survive and be productive. Although most research on longevity concentrates on the whole lifetime of an animal, it may be informative to consider factors that affect just the following years’ performance, in order to aid retention decisions, particularly when genetic information is unavailable.
Proceedings of the New Zealand Society of Animal Production, Volume 76, Adelaide, 159-162, 2016
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