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RESEARCH ARTICLE
Contents Vol 50(6)

High Merino weaner survival rates are a function of weaning weight and positive post-weaning growth rates

S. Hatcher A C , J. Eppleston B , K. J. Thornberry A and B. Watt B
+ Author Affiliations
- Author Affiliations

A Industry and Investment NSW, Orange Agricultural Institute, Forest Road, Orange, NSW 2800, Australia.

B Tablelands Livestock Health and Pest Authority, PO Box 20, Bathurst, NSW 2795, Australia.

C Corresponding author. Email: sue.hatcher@industry.nsw.gov.au

Animal Production Science 50(6) 465-472 https://doi.org/10.1071/AN09187
Submitted: 8 December 2009  Accepted: 14 April 2010   Published: 11 June 2010

Abstract

Survival and subsequent productivity of Merino ewe weaners (weaned in 2006 and 2007, respectively) on commercial properties in the New South Wales Central Tablelands were monitored through routine liveweight measurement until weaning of their own progeny from their maiden joining. Growth rates were calculated from the regular liveweight measurements with survival determined by the continuing presence of an individual animal at subsequent measurements. This study demonstrates that high weaner survival rates are a function of both weaning weight and post-weaning growth rates. Importantly, it indicates that low post-weaning growth rates can negate the survival benefit conferred by a high weaning weight such that weaners who were unable to sustain positive post-weaning growth rates were at high risk of death. Furthermore, classification of weaners into liveweight profile groups based on their weaning weight and post-weaning growth rates identified another group of weaners that are also at high risk of death. These weaners (14% of the mob) had above average weaning weights but low post-weaning growth rates and a mortality rate nearly 1.5 times that of the lightest cohort of weaners. High weaner survival rates about the 95% industry benchmark are possible if weaners show positive growth rates post weaning. Weaning weight continues to have a residual influence on the subsequent productivity of ewe weaners until they wean their first lambs. Maiden ewes that were heavier at weaning tend to have higher scanning percentages and are more likely to successfully rear their progeny to marking than their lighter weight counterparts. This finding should be taken into account when economic analyses of the benefits of alternative management strategies to promote weaner survival are undertaken.


Acknowledgements

We acknowledge the support and enthusiasm of the owner/managers of the commercial properties involved in the Tablelands Livestock Health and Pest Authority (LHPA). Without their cooperation, enthusiasm and support this project would not have been possible. Other LHPA staff and I & I NSW support provided additional technical assistance as required during the scheduled monitoring activities on each property. The 2006 drop weaner monitoring project was sponsored by Pfizer’s Eryvac vaccine and received some financial support from Lifetime Wool project, a national project supported by Australian Wool Innovation Ltd, Department of Primary Industries Victoria, Department of Agriculture and Food Western Australia, New South Wales Department of Primary Industries, Tasmanian Department of Primary Industries and Water, South Australian Research and Development Institute, CSIRO, Austral Park: Coleraine, Billandri Poll Merino Stud, Kendenup and over 120 wool producers across southern Australia.


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