Factors affecting ewe longevity on sheep farms in three European countries

The ability to identify ewes that can outperform their contemporaries, in terms of how long they remain productive in the flock, will help towards improving flock efficiency and profitability. The main objectives of this study were to: (1) identify the main reasons for mortality or culling within diverse sheep production systems in Ireland, Norway and UK; (2) investigate the influence of early life factors on ewe longevity within each of these systems; and (3) determine whether common approaches or recommendations could be employed to improve ewe longevity. The main reasons for mortality or culling were, in addition to old age, mastitis (Irish and Norwegian sheep) and tooth loss (UK hill sheep). In each country, there were significant differences in age at last lambing due to the year the ewe was born (but in no consistent pattern), and due to her flock of birth (P < 0.05). From the Norwegian data, there was some indication ewes from younger dams lambed for the last time at a younger age, however, this trend was not seen in the Irish or UK data. Ewes born as singletons, in the Irish data, lambed for the last time at an older age than those that had been born in larger litters, although this was not observed in the other data sets. Age at first lambing and some breed proportions (proportion of Texel and Suffolk particularly) of the animal (both not fitted in the Norwegian or UK analyses) were found to have a highly significant (P < 0.0001) effect on age at last lambing in the Irish analyses. The results suggest that longevity is influenced by a range of different factors and the early life predictors investigated could not be used to provide consistent recommendations across countries, production systems and breeds that would influence ewe longevity. One common definition or solution to select ewes for longer productive life in divergent sheep flocks may not be appropriate.