Ewe culling and retention strategies to increase reproductive rates in Merino sheep
S. Hatcher A G , S. Dominik B , J. S. Richards C , J. Young D , J. Smith B , R. Tearle E , F. D. Brien E and N. Hermann FA Makin Outcomes, PO Box 8358, Orange East, NSW 2800, Australia.
B CSIRO Agriculture and Food, New England Highway, Armidale, NSW 2350, Australia.
C NSW Department of Primary Industries, Orange Agricultural Institute, Forest Road, Orange, NSW 2800, Australia.
D Farming Systems Analysis Service, 476 Tindale Road, Kentdale, WA 6333, Australia.
E Davies Research Centre, School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, SA 5371, Australia.
F CSIRO Agriculture and Food, GPO Box 1700, Canberra, ACT 2601, Australia.
G Corresponding author. Email: sue@makinoutcomes.com.au
Animal Production Science 58(8) 1545-1551 https://doi.org/10.1071/AN17813
Submitted: 15 November 2017 Accepted: 3 April 2018 Published: 7 May 2018
Abstract
The present empirical study of data from three Merino resource flocks of varying genetic backgrounds run in different environments investigated the impact of various selection strategies aimed at culling poor performers (‘passengers’) or retaining good doers (‘performers’) longer, or both, on the flock reproductive performance. Four strategies were investigated and applied either individually or in combination, to quantify their impact on the litter size, rearing type and breeding efficiency (number of lambs weaned per ewe per year) of the whole flock. The main benefit from implementing any of the strategies was a decrease in the proportion of dry ewes in each flock (1–7%). There was little difference between the single strategies of culling twice-dry ewes or culling ewes that twice lambed and lost their lambs. When retaining a cohort of older ewes, it was more efficient to select these on the basis of their lifetime reproductive performance. There was only a marginal benefit gained by combining strategies and, in some cases, a single strategy was still better in terms of breeding efficiency. Commercial producers can improve the reproductive rate of these flocks by culling twice-dry ewes on the basis of their pregnancy scan data.
Additional keywords: breeding efficiency, lifetime reproductive performance, litter size, rearing type.
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