Abstract
Introduction: Developing practices that support high standards of animal welfare is a priority for the Australian sheep industry. Post-weaning mortality is one indicator of animal health and welfare. Weaner mortality targets < 4% are recommended by industry. However, weaner mortality is not widely recorded and reported.
Research objective: To determine mortality between weaning and 12-months-of-age (weaner mortality) for Merino ewes on Australian sheep farms.
Method: Merino ewes (n = 3195; ~400–600 ewes per farm) on seven farms in Western Australia (n = 5) and New South Wales (n = 2) were monitored between weaning and 12 months-of-age. Logistic regression was used to assess the relationship between weaning weight, birth type (single, twin, triplet) and farm on weaner mortality. Odds-ratio (OR) were determined using Pearson Chi-square.
Results: Overall weaner mortality was 5.4% (range 2.3%–7.6% between farms). Weaner mortality was > 4% on 5/7 farms and > 5% on 3/7 farms. Average weaning weight was 25.7±5.7kg (mean±SD) with means ranging 21.7–30.3kg between farms. Weaning weight was confounded by farm, with farm strongly associated with weaner mortality. Odds of mortality for weaning weight were 0.96 (95%CI 0.93, 0.98; p = 0.002), meaning for every 1kg increase in weaning weight, odds of mortality decreased by 0.04. There were no associations for nutrition group or birth type with weaner mortality. Odds of mortality for ewes < 20 kg at weaning was 1.5 times that of ewes ≥20kg (OR 1.53, 95%CI 1.05, 2.22; p = 0.027).
Conclusion: Merino weaner mortality ~5% observed for contemporary Merino genotypes managed in extensive production systems was consistent with previous Australian studies from previous 20 years, but remains higher than longstanding industry targets ≤ 4%
Animal ethics: Murdoch University Animal Ethics Committee R3334/21
Acknowledgements: This study was supported with funding from Meat and Livestock Australia