Genetic Variation of Weaner Survival in Merino Sheep and Its Relationships with Growth and Wool

There is little evidence that mortality rates in Australian sheep during the period after weaning are improving over time. This paper explores the potential for producers to select to improve survival rates and the potential impact this may have on key production traits. A total of 114,272 weaner survival records were obtained from a wide variety of Australian Merino sheep types and production systems. Weaner survival, a binary dependent variable, was analysed as a continuous trait using a sire model. The heritability of weaner survival was estimated at 0.05 ± 0.01, significantly greater than zero. The survival of weaned lambs to yearling age was influenced by weaning weight with higher survival rates observed in heavier lambs (rg = 0.14). Weaner survival adjusted for weaning weight was found to be antagonistically genetically correlated with fleece weight (rg = -0.12 to - 0.24). Due to antagonistic genetic correlations with greasy fleece weight and other production traits, producers should record weaner survival which will assist Sheep Genetics to produce breeding values and incorporate weaner survival in future indexes.