Defining longevity and estimating genetic parameters in Australian Merino ewes

Abstract

<p>Currently, there are no measures of ewe longevity recorded by Australian sheep breeders for utilisation as part of their breeding objective. In the absence of disposal codes, this study explored the potential to use production records to define ewe longevity in Merino sheep and estimate genetic parameters for the resulting trait. The longevity trait was defined as the ewe's total life (TL) in the flock from birth to their last available production record. To identify suitable non-censored data, cohorts were selected based on the amount of pedigree and consistent annual production recording. Under these assumptions, the MERINOSELECT database provided 267,517 longevity records from 143 flocks. The heritability of TL was 0.22 ± 01. Adjusting TL for the ewe's lifetime reproductive performance, accounted for 94% of the variation in TL, reduced the heritability to 0.11 ± 01. The results herein indicate that it is possible to describe longevity in the Merino ewes using production records from the MERINOLSELECT database. TL was found to be heritable but further exploration is required before incorporation in industry breeding objectives.</p>