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RESEARCH ARTICLE
Contents Vol 46(7)

Selection response in fecal worm egg counts in the Rylington Merino parasite resistant flock

L. J. E. Karlsson A B and J. C. Greeff A
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- Author Affiliations

A Department of Agriculture and Food WA, 10 Dore Street, Katanning, WA 6317, Australia.

B Corresponding author. Email: jkarlsson@agric.wa.gov.au

Australian Journal of Experimental Agriculture 46(7) 809-811 https://doi.org/10.1071/EA05367
Submitted: 22 December 2005  Accepted: 21 May 2006   Published: 8 June 2006

Abstract

The Rylington Merino internal parasite resistant selection line was initiated in 1987 from a wide genetic base of 100 ewe flocks. Selection for parasite resistance was based on selecting animals with a low worm egg count in a natural parasite challenge environment. The realised annual genetic gain for estimated breeding value of worm egg count is 2.7%. The genetic gain in parasite resistance has been achieved without any adverse genetic correlations with the other economically important production traits. There is an unfavourable genetic correlation between worm egg count and scouring traits. The recommendation to industry is to select for both low worm egg count and reduced diarrhoea and combine these traits with other economically important production traits. The relative weighting applied to each component trait will vary according to the local parasite challenge situation and the time frame available to achieve sustainable parasite control.


Acknowledgments

This long-term selection line has had various funding support including; wool producer research funding through Australian Wool Corporation and the Department of Agriculture WA. The initial ewe and ram contributions by sheep farmers and research organisations are acknowledged. Richard Coole and other farmers associated with Rylington Merino have provided assistance to the running of this project. Departmental staffs at research stations and laboratories have helped. Numerous scientific colleagues have collaborated.


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