Using partial records to identify productive older ewes to retain in the breeding flock to increase the flock net reproduction rate
G. J. Lee C , M. A. Sladek A B , S. Hatcher A B D and J. S. Richards A BA CRC for Sheep Industry Innovation, Homestead Building, UNE Armidale, NSW 2351, Australia.
B NSW DPI, Orange Agricultural Institute, Locked Bag 6006, Orange, NSW 2800, Australia.
C Formerly NSW DPI, Orange Agricultural Institute, Locked Bag 6006, Orange, NSW 2800, Australia.
D Corresponding author. Email: sue.hatcher@dpi.nsw.gov.au
Animal Production Science 54(10) 1631-1634 https://doi.org/10.1071/AN14435
Submitted: 24 March 2014 Accepted: 17 June 2014 Published: 19 August 2014
Abstract
The reproductive performance of 7286 ewes from three Merino genetic resource flocks maintained in the central-western region of New South Wales was used to compare the use of fertility and fecundity information and net reproduction information whether recorded early (at 2 and 3 years of age) or later in life (at 4 and 5 years of age) with lifetime performance (at 2–6 years of age) as alternative selection criteria to identify productive older ewes to retain in the breeding flock. While the lifetime net reproduction rate is the best indicator of a ewe’s reproductive performance in later life, producers basing their selection decisions on pregnancy scanning data, which provides information on both fertility and fecundity, can improve the net reproduction rate of their flock by 2% regardless of the base reproduction rate. Despite little difference in likely flock reproduction rates between using early or later life scanning information as the selection criteria, early life performance is the best choice for commercial producers because it provides scope for eliminating twice-dry ewes from the breeding flock early in life, especially when combined with udder examination at marking.
Additional keywords: pregnancy scanning, selection criteria, udder examination.
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